FV FAIRVALUE CALCULATOR · The Fair Value Playbook
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Fairvalue Calculator · 2026 edition

The Fair Value Playbook

An evidence-based handbook for calmer investing — what a stock is really worth, why the gap is your opportunity, and the science that says it works.

Dr. Peter Klein, Founder Dr. Peter Klein, BAFounder · fairvalue-calculator.com

A practical, scientific guide to value, quality, profitability and mean reversion — built on the live Fairvalue Calculator method.

Educational research only. Not financial advice. Historical data and backtests are not guarantees of future results.

Tip: use the Download PDF button (top right) to save this handbook. It prints cleanly in the dark theme.

Part I · Foundations
Chapter 1 · Introduction

Why this handbook exists

The idea in one sentence — and who it's for

I did not originally write this for the market. I wrote it for my children, Rosalie and Ferdinand, and for the younger version of myself who sensed that something important was happening in investing but could not find a simple, honest, practical explanation.

For a long time the stock market looked like a strange game. Some people treated stocks like gambling; others spoke as if professionals had a secret language ordinary people could never learn. I had no mentor, so I learned the slow way — books, mistakes, spreadsheets, painful lessons, and eventually a system.

One sentence organised the whole subject for me: price is what you pay, value is what you get [18]. On a screen you see prices every second. What you do not see directly is value. If you never estimate value, your decisions quietly become emotional — fear, greed, hope, panic, or the feeling that you're missing out.

That is why I built the Fairvalue Calculator. It is not magic and not a promise. It is a compass. It asks one clean question: is this stock probably cheap, fair, or expensive compared with a reasonable estimate of its intrinsic value? This handbook turns that question into a repeatable process — and shows you the science that says the process has an edge.

Core principle

You do not need a finance degree. You need clarity, rules, patience, and a way to separate emotion from decision.

Chapter 2

Why monkeys often beat fund managers

Costs, incentives and the private-investor edge

When you ask a bank to invest your money, you are often sold a feeling before you are sold a strategy. The key question is not how elegant the fund name sounds — it is what costs you pay, and who gets paid regardless of performance.

Active funds face two structural problems. First, incentives aren't always aligned: institutions may prefer their own products or whatever is easiest to sell. Second, size is a cage — a fund moving billions cannot turn as nimbly as an individual managing a personal portfolio.

The maths is unforgiving. William Sharpe's "arithmetic of active management" [19] shows that, before costs, the average actively-managed dollar must earn exactly the market return — so after fees, the average active dollar must underperform the market. Decades of SPIVA scorecards from S&P confirm it: across most regions and horizons, the majority of active funds trail their benchmark [S1]. Carhart showed that what little persistence exists is largely explained by costs and momentum, not stock-picking genius [20].

This does not make professionals useless. A low-cost index ETF is a perfectly sensible core. But if you choose individual stocks, you need something a brochure cannot give you: a process that stops you confusing price movement with business value. That is exactly where this method begins — and where a disciplined private investor actually holds an edge over a giant, fee-laden fund.

Practical takeaway

Before buying any fund or stock, ask: what are the costs, what is the underlying value, and can I explain the decision without relying on somebody else sounding confident?

Chapter 3

Price is not value

Mr. Market, the margin of safety, and your real edge

A stock price is only the last transaction between two participants. It is not an objective truth about the company. In real life you would never buy a house just because yesterday's quote jumped — yet in stocks, people do exactly that, because the market flashes prices in their faces all day.

Benjamin Graham gave us the antidote: imagine the market as a moody business partner, Mr. Market, who shows up every day quoting a price to buy your share or sell you his. Some days he is euphoric, some days terrified. You are free to ignore him — or to exploit him — but never obliged to trade [18]. Fair value is your anchor against his moods. It is not a prophecy; it is a rational estimate, or range, that sorts a stock into three zones: undervalued, fairly valued, overvalued.

PRICE vs. TRUE WORTH FAIR VALUE $118 +90% VALUE GAP PRICE TODAY $62 FUTURE
The core idea behind the tool: the gap between today's price and a defensible estimate of fair value is the potential upside — your margin of safety. (Illustrative.)

This changes how you feel about volatility. A falling price can be a warning — or an offer. It depends entirely on value. But the anchor only works if it is honest: the more stable the earnings, the cleaner the growth, and the stronger the balance sheet, the more useful a fair-value estimate becomes. The shakier the business, the wider the range and the larger the safety margin must be.

Evidence note

This is not folklore. The "value effect" is among the most-replicated facts in finance: Basu showed high earnings-yield stocks earned higher risk-adjusted returns [1]; Fama & French showed book-to-market captures much of the cross-section of returns [2]; Lakonishok, Shleifer & Vishny tied it to investor overreaction [3]; De Bondt & Thaler documented the long-term reversal that follows [4].

Part II · The Method
Chapter 4

The simple Fair Value calculator

EPS, growth, smoothing and guardrails

The simple calculator has one job: teach the logic of fair value without intimidating you. You enter earnings per share and a growth rate, and the output forces a conversation between today's price and a reasonable estimate of worth.

EPS is profit per share — preferably diluted EPS, which accounts for options and other instruments. Growth should come from observed or carefully estimated revenue/earnings growth, not from hope. If revenue rises from 100 to 110, that's 10% — nothing mystical.

The biggest beginner mistake is treating a single abnormal year as normal. A one-off gain, a write-down, a cyclical spike or a crisis year can make a valuation look mathematically clean but economically wrong. That is why smoothing matters — median, mean, geometric and weighted averages reduce the influence of one-off distortions and move you toward a sustainable base level of profit and growth. (Our live engine uses a weighted, robust growth blend for exactly this reason.)

Rule

If the input is unrealistic, the output is not analysis — it is speculation dressed as mathematics. Companies with no profits, extreme growth assumptions or chaotic history should not be forced into a simple formula. Sometimes the best output is a warning, not a number.

Chapter 5

Finding ideas — tools and everyday life

From stories to verifiable candidates

Good ideas come from screeners, magazines, conversations, everyday products — even your children or partner noticing a brand everywhere. The art is not finding stories. The art is testing them.

The database and screener turn a spontaneous idea into a structured candidate: filter for stocks whose calculated fair value sits above the current price, then narrow by region, size, profitability, debt, growth and trend. This stops you confusing media attention with investment quality.

Everyday life still matters — the early iPhone was a product signal millions saw as consumers before they understood it as investors. A great product can reveal customer love, pricing power and room to grow. But you must take one more step: check whether the numbers support the story. A company can be beloved and overvalued; a boring one can be ignored and deeply cheap.

Question for every idea

Is this just a great story, or is there a measurable gap between price and value? Let curiosity fill the funnel — but let data decide what stays.

Chapter 6

The tools, explained

Search, radar, stock page, watchlist, portfolio — one workflow

The Premium Tools are a shortcut through work you could do by hand across dozens of websites and spreadsheets — but the real value is that the process becomes repeatable.

The stock card — a verdict at a glance

Every stock in the radar is a card: the company, its estimated fair value, the live price, the resulting upside, a Quality Score (how good the business is) and an Evidence rating (how much data backs the estimate).

EXMPL · Example Corp. FAIR VALUE $118 PRICE $62 UPSIDE +90% QUALITY 72/100 EVIDENCE High Undervalued · cheap price, strong business, well-supported estimate → a candidate worth a closer look.
Anatomy of a radar card: Fair Value vs. Price gives the upside; Quality grades the business; Evidence grades the data behind the estimate.

From the whole market down to one decision

The dashboard is the control center; the screener is the discovery engine (filter thousands of companies by value gap, quality, debt, growth and strength); the stock page is the dossier (fair-value models, history, sector comparison, quality indicators); the watchlist is where discipline lives — you watch whether price and value converge before you act; and the Portfolio Manager adds the layer most private investors ignore: diversification across region, sector, size and cash.

A repeatable funnel Market cheap / fair / rich? Sector where's the value Screen candidates Stock Watchlist · Portfolio Repeat. The more often you follow the same path, the less power daily noise has over you.
Quality adjustment

Strong, stable companies deserve more trust in the valuation; weak or chaotic ones need a larger discount. A stock that looks "200% below fair value" but has unstable numbers can be less attractive than one with a smaller gap and much cleaner fundamentals. The goal is never to worship the score — it is to see where the opportunity and the risks actually are.

Chapter 7

The method in practice

Market → sector → stock → portfolio

The method is top-down, then bottom-up. First, classify the market — if broad valuations are high you become selective and keep cash for better opportunities; if they're depressed after a crisis, you can justify more risk. This is not magical market timing; it is risk budgeting.

Second, read the sectors — some are cheap for good reasons, others expensive for bad ones. Third, screen for undervalued names. A good candidate has fair value above price, acceptable quality, manageable debt, sufficient liquidity and no obvious data red flags; a better one adds stable revenue, consistent earnings and a trend that isn't collapsing. Fourth, inspect each company's dossier. Fifth, build and maintain the portfolio.

Portfolio logic

A stock can be attractive on its own and still be a bad addition if it makes the portfolio too concentrated in one sector, one country or one story. You build portfolios, not heroic one-stock bets.

Chapter 8

Timing, exits and money management

A strategy becomes real only through rules

The perfect entry is usually an illusion. Waiting forever for the absolute bottom can hurt as much as buying everything at once at the top. Treat entry as a process: when the market is expensive, build positions gradually and hold reserves; when it cheapens, add risk in a controlled way. Cash becomes an option, not a permanent fear position.

Fair value is not tomorrow's target price — it is a multi-year orientation. Many value effects need three to five years to unfold, and our own evidence points to a similar horizon (Frankel & Lee found the value-to-price signal pays over ~3 years [6]). If you cannot hold through several difficult years, the method will feel far harder than it looks on paper.

Exits need rules too. There are three honest reasons to sell: you need the money, the investment case breaks, or the position no longer fits the portfolio. A falling price alone is not a reason. A falling price plus deteriorating fundamentals, a lower fair value and a broken trend is.

Money-management rule

Cut broken cases — when the fair-value thesis is gone, price is below its long moving average and the position is already negative. Do not cut winners only because they finally work, or only because they make you nervous. Let strong businesses compound while value, quality and trend still support them.

Chapter 9

Psychology and the forgotten portfolio

The hardest part of investing is not the formula

The most dangerous opponent is not the market — it is your own mind. Behavioural finance exists because humans repeat the same mistakes: we sell winners too early because locking in a gain feels good, hold losers too long because admitting an error hurts, chase hype because others seem to get rich faster, and panic in crashes because headlines turn fear into a social experience.

Kahneman & Tversky's prospect theory explains much of it: we feel a loss roughly twice as intensely as an equivalent gain, which pushes us to take the wrong risks at the wrong times [21]. Fair-value thinking helps because it hands you a reference point. You don't just see that a price fell — you see whether it fell below value, whether value itself changed, or whether the thesis is simply broken.

Two personal lessons. Penny stocks with wonderful stories and terrible substance taught me that a low share price is psychologically seductive (you can buy "so many") but not safer. Leverage taught me that products which make the first win feel brilliant make the first big loss feel impossible — they raise the emotional temperature until a portfolio becomes a casino. The strongest lesson came from a nearly forgotten portfolio of solid companies, left alone for years to compound. Patience and process quietly beat clever activity.

Psychological edge

A rule-based process does not remove fear and greed. It gives you something stronger to hold onto when they appear.

Part III · The Science
Chapter 10

Fair Value, deeply

The models, and why it's a range, not a point

Behind the single number on a card sits a family of models, not one formula. Earnings-power and P/E-based views, cash-flow and DCF logic, asset/book views, dividend logic, and EV/EBITDA multiples each look at the same business from a different angle. We blend them — family-balanced, weighted by the company's growth profile — into a consensus bear / base / bull range. A wide range is information: it tells you the business is hard to pin down and demands a bigger margin of safety.

Two disciplines keep the number honest. Scale & unit sanity rejects fundamentals that are off by a factor of a thousand or quoted in the wrong currency sub-unit, before they can poison a valuation. Robust growth uses weighted, outlier-resistant trends so a single freak year cannot dominate. And a plausibility gate withholds anything whose output is mathematically possible but economically absurd — a fair value ten times the price is treated as a data problem to verify, not a signal to celebrate.

Why a range beats a point

A precise wrong number feels scientific and is dangerous. An honest range — anchored to stable fundamentals, widened for shaky ones — is what actually protects capital. Fair value is an orientation, not a prophecy.

Chapter 11

The Quality factors and their science

Every factor we use — and the peer-reviewed paper behind it

"Cheap" alone is a trap. The graveyard of investing is full of stocks that were statistically cheap and deserved to be. That is why every company also earns a Quality Score, built from factor families that each rest on decades of peer-reviewed evidence. Crucially, we did not invent these signals — we selected the ones that replicate. Here is the full map, factor → finding → source.

Factor family (what we compute)What it capturesScientific basis
Value — earnings yield, book-to-market, sales & FCF yield, EV/EBITDACheap relative to fundamentals tends to outperform.Basu (1983) [1]; Fama & French (1992) [2]; Lakonishok–Shleifer–Vishny (1994) [3]
Quality / Profitability — gross profitability, ROA/ROE, marginsHighly profitable firms earn higher future returns.Novy-Marx (2013) [7]; Fama & French five-factor (2015) [9]; Asness–Frazzini–Pedersen "Quality minus Junk" (2019) [8]
Fundamental strength — F-Score, solvency, coverageFinancially strong firms avoid the distress that kills cheap stocks.Piotroski (2000) [5]; Altman Z-Score (1968) [17]
Earnings quality — accruals, manipulation screenCash earnings beat paper earnings; flags aggressive accounting.Sloan (1996) [15]; Beneish M-Score (1999) [16]
Intrinsic-value reversion — value-to-pricePrice drifts back toward model-based intrinsic value.Frankel & Lee (1998) [6]; De Bondt & Thaler (1985) [4]
Momentum — 3/6/12-month, 52-week-highRecent relative strength tends to persist for months.Jegadeesh & Titman (1993) [10]; George & Hwang (2004) [11]
Low risk — low volatility, low betaLower-risk stocks have earned better risk-adjusted returns.Ang et al. (2006) [12]; Frazzini & Pedersen (2014) [13]
Conservative investment — asset-growth restraintFirms that don't over-expand tend to outperform empire-builders.Titman–Wei–Xie (2004) [14]; Fama & French (2015) [9]

On a stock page these become a transparent set of bars — you can see why a company scores well or badly, and the academic basis is named on every family.

Quality Score 72/100 — by factor family Profitability Fundamental strength Value Momentum Low risk
Illustrative quality bars on a stock page — each family is scored and traceable to the literature above. The AI-Quality layer adds a qualitative read of competitive moat on top of these quantitative factors.
The combination is the point

Value tells you it's cheap. Quality, strength and earnings-quality tell you it's cheap for a good reason or a bad one. Asness–Frazzini–Pedersen showed that "quality minus junk" earns significant risk-adjusted returns in the US and internationally [8] — exactly why we never screen on cheapness alone.

Chapter 12 · Evidence

How we proved it works

Our backtests, mapped onto the academic record

A strategy deserves trust only if it has a reason to work and that reason shows up in data. Our evidence rests on three pillars: the peer-reviewed literature above, our own long-term observations, and an implementation that never relies on a single formula. Here is what our internal studies found — stated honestly, including the spread.

83%of undervalued stocks reached fair value within ~5.5 years
~5 yrsmedian time to converge (100-stock study since 2015)
+846%32 stocks flagged undervalued in 2005 → Aug 2025
+162%the broad market over the same period

Mean reversion takes time — a survival curve

Share not yet at fair value 100%75%50%25% median ≈ 5 yr 02468 years held
Time for price to converge to fair value: a median of about five years (100-stock study since 2015); ~83% within ~5.5 years in our model. Illustrative of the convergence pattern.

The average is strong — but the spread is the truth

How the 32 stocks did · total return 2005 → Aug 2025 avg +846% vs market +162% number of stocks 9Loss 50–100% 6100–300% 5300–800% 6>800% ▲ median +180% incl. one at +14,514%
The honest picture: the average +846% beat the market's +162%, but outcomes are very uneven — 9 of the 32 lost money, the typical (median) stock made +180%, and a few outliers lift the average far above the median. This skew is exactly why diversification matters.

The edge concentrates early

Extra return p.a. by holding period ≈ +9% p.a.Years 1–5 Years 6–10 Years 10+
The advantage is largest in the first ~5 years (≈ +9% p.a.) while price converges to value, then flattens but stays positive. Patience captures it; impatience throws it away. Illustrative of our long-term study.

Mean reversion is not one pattern

Sometimes the price rises to meet a steady fair value; sometimes the fair value falls to the price; sometimes fundamentals grow into a flat price; often both move toward each other. The convergence is real — the path varies.

A · Price → value
B · Value → price
C · Fundamentals rise
D · Both converge

Mapped onto the literature, the picture is consistent: low valuation [1][2][3], quality and profitability [5][7][8][9], and mean reversion / intrinsic-value convergence [4][6] have all historically mattered. Piotroski's fundamental signals added ≈7.5% p.a. to value-stock returns over 1976–1996 [5]. Our internal results sit in the same family of findings — strong on average, wide in dispersion.

Read this honestly

These are internal, hypothetical backtests and historical samples, not peer-reviewed results, and they can suffer from survivorship bias, look-ahead bias, costs and taxes. A high average hides real losers. The correct conclusion is not "this is easy" — it is "this is a statistically supported framework for decisions under uncertainty." Past performance does not guarantee future results.

Chapter 12b

Case studies — from undervalued to today

What the value gap looked like in the wild

Numbers in the aggregate are convincing, but a single story makes the idea concrete. Here are real names the value lens looked at when they were out of favour — and where they trade now. Read them honestly: they are chosen with hindsight to show what the method looks for, they are not buy recommendations, and they are not typical. For every winner there were stocks that went nowhere or fell — the honest average and its wide spread are in the previous chapter.

Meta Platforms — the market priced in permanent decline

In an October 2022 article we worked through Meta (then Facebook) as a teaching example. The stock had collapsed to about $129 — down roughly 70% from its peak — as the market extrapolated falling profits and heavy spending into permanent decline. But the fundamentals told a different story: enormous cash flow, a dominant advertising franchise, and a balance sheet that could fund the experiment. Price had detached from value, which is exactly the gap the method hunts.

By mid-2026 Meta traded near $600 — a gain of roughly +365% from that low. The lesson is not that we predicted it; it is that when a sound business is priced for catastrophe, the gap between price and value is where patient money is made.

$129 Oct 2022 $600 mid-2026 · +365%
Meta Platforms (META): from about $129 in late October 2022 to about $600 by mid-2026 — roughly +365%. Prices from our own price history; illustrative, not advice.

Two more from the same period

Goldman Sachs — featured around $297 in late 2022, near $1,091 by mid-2026 (about +268%). Apple — around $145 in late 2022, near $299 by mid-2026 (about +107%).

The same pattern shows up over much longer horizons. In our 2005 cohort, 32 stocks flagged undervalued returned on average +846% by 2025 versus +162% for the market — with Goldman Sachs the extreme outlier at roughly +14,514%. But 9 of those 32 lost money. The average is strong; the spread is the truth.

How to read these honestly

Case studies are selected after the fact and make the method look easy — it is not. Prices are point-in-time (from our own price history, mid-2026), past performance does not repeat, and value can stay cheap for years. The point of a case is to show what the value gap looks like in the wild — not to promise the next one.

↑ Back to top
Chapter 13

Why we leave everything else out

The factor zoo, and the discipline of less

If value and quality work, why not add fifty more signals? Because most "signals" are noise wearing a lab coat. Academics now describe a "factor zoo" of hundreds of published predictors — and when Harvey, Liu & Zhu re-examined them with proper statistics, they argued that most should be viewed with deep suspicion: test enough variables and some will look significant by pure luck [22]. Hou, Xue & Zhang found that a large share of published anomalies simply fail to replicate once you correct for obvious flaws [25].

It gets worse after publication. McLean & Pontiff measured that predictability decays by roughly half once a factor is published and arbitraged [23]. And Bailey, Borwein, López de Prado & Zhu showed that with enough trials you can always produce a beautiful backtest that is pure overfitting — "pseudo-mathematics" [24]. A clever-looking strategy is often just a story fitted to the past.

So we apply a hard filter. We keep a factor only if it is (1) economically motivated — there's a reason it should work; (2) replicated across decades, countries and asset classes; and (3) survives out-of-sample, not just in the window where it was discovered. That leaves exactly the families in Chapter 11: value, quality/profitability, fundamental strength, earnings quality, intrinsic-value reversion, momentum, low-risk and conservative investment.

What we deliberately do not do — and why

We leave out…Because, statistically…
Chart-pattern "astrology", most technical signals in isolationLittle robust out-of-sample evidence; easy to overfit; not economically motivated.
News/hype and tip-chasingAlready in the price by the time you read it; a negative-sum game after costs [19].
A single "magic" ratioOne metric is fragile and gamed; the edge is in the combination of value + quality.
Day-trading & market-timing magicCosts and taxes dominate; the average active dollar must trail the market [19][20].
Leverage & penny-stock lottery ticketsRaise ruin risk and emotional temperature without raising expected return.
Dozens of correlated "factors"The factor zoo: most don't replicate and decay after publication [22][23][25].
The discipline of less

Complexity feels sophisticated and quietly destroys returns. We would rather own a handful of effects that have survived fifty years of scrutiny than a hundred that survived one backtest. Less, done honestly, is the edge.

Chapter 14 · Conclusion

What remains when the noise fades

The method in one calm picture

Turn down the volume and the method becomes simple. Separate price from value. Buy only when value, quality and a margin of safety line up. Diversify. Hold long enough for the thesis to work. Review with rules. Sell when the case breaks — not when the headline is loud.

The process is not built to eliminate losses; it is built to stop isolated mistakes from becoming fatal. Fair value reduces the risk of paying for fantasy. Quality reduces the risk of buying a trap. Diversification reduces the risk of one wrong company destroying you. Time gives good businesses room to compound.

A rules-based approach also changes your emotional life. A crash becomes an environment to classify, not a reason to panic. A hype stock becomes a story to test, not a command to buy. A falling holding becomes a question — is fair value still intact? A rising winner becomes another — has the gap closed, or is the business still compounding?

Final word

You don't need to be a genius. You need a process you can explain and repeat — knowing what you own, why you own it, when the case is broken, and how each position fits the whole. The goal is not to predict every move. It is to make better decisions, often enough, calmly enough, and long enough for probability to work in your favour.

Part IV · The Origin
Chapter 15

Where this method comes from

A boy in Graz, a hundred books and a green lamp

Everything in this handbook has a history, and I think you should know it before you trust the method. It did not start in a bank or at a fund. It started in 2004 in Graz, Austria, when I was fourteen and could not get one question out of my head: how is it possible that a few investors build wealth with stocks decade after decade, while friends and relatives call the stock market a place where you lose house and home?

I answered the question the slow way. Over the next sixteen years I read more than a hundred books about the stock market, ordered one by one online. In the handbook I wrote in 2020 I did the sum: the books cost about 5,000 euros, and the same money put into the shares of the bookseller in 2004 would have multiplied about a hundred times. Education pays the best interest, people say. In this one case the shares would have paid more.

Two expensive lessons

At eighteen I made quick money with a single stock and decided I had a talent. I moved on to leveraged certificates, read candlesticks, trend lines and oscillators on several time frames, and refreshed the index on my phone even in the bathtub. Then the account was empty. That was lesson one: leverage and constant trading are a way to transfer money to the issuer.

While I licked my wounds I remembered a demo portfolio I had opened after a school stock market game: a handful of blue chips, bought once and forgotten. I reset the password and looked. It had roughly quadrupled between 2004 and 2008 without a single decision from me. The forgotten portfolio had beaten all my clever activity by a wide margin.

Lesson two came in the financial crisis. I rebuilt my portfolio with jobs and pocket money, watched it fall in 2008, and bet on falling prices almost exactly at the low. The market turned and the savings were gone a second time. Since then I do not use leverage and I do not try to time the market. Chapter 9 of this handbook grew out of those years.

The green lamp

After school and civilian service in a hospital I studied dentistry, like my father, and I run a dental practice today. The stock market never let go of me. In my student flat, a dark place with windows on one side only, I built a small office from a coffee table, a chair and a lamp with a green shade, the kind you would expect in a law firm. I called it the thinkers club lamp. Under it I read annual reports, hundreds of them.

Reading annual reports is nobody's hobby, and without a business degree most of the numbers stay closed. But if you want to know what a company is worth, there is no way around them. Every established valuation method I studied had its merit, and all of them had one thing in common: hard to learn and hard to apply for a normal person. So I looked for a way to get from a few reported numbers to a reasonable estimate of value, fast, and to test honestly whether it works.

I combined figures from the reports into formulas, first on paper. Calculating every stock by hand became tedious, so I had the formulas programmed and put the calculators on a website. That website is the reason this book exists.

In one sentence

I built the Fair Value Calculator for myself first. It was never the plan to sell anything. I needed more and more tools, hired programmers, and decided it would be a pity if nobody else could use the method.

Chapter 16

Ten years in public: the dated record

What was built when, each line with its source

Many products claim a long history. Ours can be checked. On 20 March 2016 fairvalue-calculator.com went online, and one day later I presented it in a large German investor forum and asked the members to test it. That thread still exists. It has grown to eight pages over ten years, and it contains what no company history written afterwards can offer: dated posts, concrete numbers, mistakes found by strangers, and my answers at the time.

The list below follows that record. After each line you see what kind of source carries it: a publication dated in public at the time, the handbook I published in 2020, or my own account where no outside record exists. The numbers in brackets point to the list of sources at the end of this part.

2004Aged 14 in Graz, Peter Klein starts studying stocks and reads more than a hundred investing books over the following years. handbook 2020 [S9]
2004 to 2009Apprentice years: losses with leveraged certificates, a forgotten demo portfolio of blue chips that quadruples between 2004 and 2008, and a lost short bet at the bottom of the financial crisis. The conclusion: long-term investing by value. handbook 2020 [S9]
2013During his studies he writes his own valuation formulas by hand and runs first backtests. This is his own account; there is no public third-party record dated 2013. own account [S9]
20 March 2016fairvalue-calculator.com goes online: a free calculator that estimates intrinsic value from earnings per share and growth, based on an extended Graham formula tuned to approximate a discounted cash flow valuation. dated in public at the time [S1]
21 March 2016Public launch post in the German Wertpapier-Forum (user name petz00711), asking for tests. The very first post already invites users to publish their calculated fair values so that other investors can find new ideas. dated in public at the time [S1]
21 to 26 March 2016Forum members test the calculator at once and find weaknesses: too little openness about the formula, implausible results for very small earnings, the stock split problem, and two inputs being too few for cyclical companies. On 22 March the calculator is adjusted for small earnings. dated in public at the time [S1]
30 March 2016Start of the public wikifolio "Fair Value Calculator": a public model portfolio run by the method; the creation date is recorded by the provider. dated in public at the time [S10, S9]
3 June 2016First larger backtest published in the forum (33 German and US stocks, 2005 to 2015). A self-run study on a small sample, rightly questioned in the forum; today replaced by the 34-year test, adjusted for companies that no longer exist. dated in public at the time [S2]
12 to 15 June 2016Three helper calculators (weighted earnings, linear and weighted growth), a tutorial video and a first indicator showing whether the whole market is over- or undervalued. dated in public at the time [S3]
15 September 2016New website with database and hotlist: users enter fair values, much like Wikipedia, and check each other. First list of 18 stocks that appear undervalued. dated in public at the time [S3]
19 July 2017Community database with more than 100 entries, an automatic hotlist and a way to report wrong values (three reports trigger a review). dated in public at the time [S3, S4]
8 May 2019Relaunch after two years of development: automatic valuation from a large database, screener, watchlist, two languages, plus a premium area for diversified portfolios. dated in public at the time [S4]
4 December 2019Detailed calculator in answer to the criticism "two inputs are too few": earnings growth, profitability, revenue growth, return on equity, EBIT margin and book value now feed in, weighted by his own statistical analysis. dated in public at the time [S4]
18 March 2020After criticism of data quality and cyclical stocks: smoothing by median and geometric mean, a warning for highly leveraged companies, stars for data quality, a freshness indicator. dated in public at the time [S5]
2020The handbook "Die Fair Value Calculator Methode" (77 pages) documents the method and the tools: automatic fair values for more than 33,000 stocks, market analysis, sector analysis, quality check, total score, watchlist and portfolio manager. handbook 2020 [S9]
24 July 2020Discounted cash flow and the PEG ratio are integrated as further valuations. dated in public at the time [S6]
8 January 2021Several valuation methods are computed automatically and combined into one fair value. A video series of six lessons follows. dated in public at the time [S6]
14 November 2021Star ratings from fundamentals and price trend, industry comparison for every metric, a reworked market view. dated in public at the time [S6]
21 April 2022Free version: all tools and five stocks a month at no cost. Mobile optimisation follows in June 2022. dated in public at the time [S6]
16 March 2024The model blend is explained openly: more than twelve methods, among them DCF, analyst estimates, peer multiples, Peter Lynch and Graham. The sentence that goes with it: "There is no single correct fair value, but there are many methods to get as close to it as possible." dated in public at the time [S6]
8 September 2025AI valuation for soft factors: brand strength, management quality, competitive advantages and scalability complement the numbers. dated in public at the time [S6]
28 July 2026In its tenth year, the complete rebuild: about 35,000 stocks worldwide, valuation and quality as two separate questions, a range from cautious to optimistic case, an evidence status per stock, a portfolio optimizer and a 34-year test. dated in public at the time [S6, S7]
August 2026Public corrections after hints from the forum: an error with one-off losses (Amazon, Rivian) is fixed, the cap on downside potential at 80 percent is removed, the search finds stocks by name, ISIN, German WKN and ticker. dated in public at the time [S7, S8]
October 2026Current state: 26 valuation models, up to 37 quality factors, about 35,000 valued stocks, an AI verdict with the main risk per stock, user comments and votes, a free academy of 16 lessons and a connection for AI assistants. own account [S11]
In one sentence

Publicly documented since 20 March 2016: grown from a self-developed online calculator into a global platform for fair value and quality over more than ten years.

One detail from the first post matters to me. It already asked users to publish the fair values they had calculated, so that other investors could discover new ideas. The comments and votes you find on every stock today are that same thought, ten years later.

Chapter 17

What the critics changed

Why the public arguments are the best part of the record

The forum was not kind. Within hours members called the formula a black box, demanded statistical proof, found a problem with stock splits and pointed out that two inputs cannot value a cyclical company. They were right more often than I liked at the time.

I keep these arguments in this handbook on purpose. A history that only shows applause proves nothing. A history in which outsiders find errors and the product changes in response is hard to invent afterwards. Here are the main objections and what became of them.

YearThe objectionWhat became of it
2016The formula is a black box; proof needs a hundred stocks and more than ten years. [S1]Today the methodology is published on the site, the test covers 34 years and is adjusted for companies that no longer exist.
2016Two inputs (earnings and growth) are not enough for cyclical companies and tough industries. [S1]Two inputs became 26 models weighted by industry, plus a separate quality score from up to 37 factors.
2016A stock split changes the result, which must not happen. [S2]Every figure is computed per share on the current share count, splits are checked and adjusted daily.
2020The best formula is useless if some of the underlying data is wrong. [S5]Every stock carries an evidence status. Where the data is too thin, the fair value is withheld rather than showing a wrong number.
2020Return on equity misleads when debt is high; return on capital employed is better. [S5]Balance sheet strength is a family of its own in the quality score, high leverage is scored and shown, and return on invested capital is available in the screener.
2026Growth stocks look permanently overvalued. [S7]The fair value stays deliberately sober ("a yardstick, not a price target"); in return the site shows openly how much growth the price assumes, and a documented premium for quality growth was added.
Honest note

About the early numbers: the backtests I posted in 2016 and printed in the 2020 handbook were my own studies on small samples. They showed that the idea deserved more work. They were not proof. The figures in Chapter 12 come from the later 34-year test, adjusted for companies that no longer exist, and they too are historical results, not a promise.

Chapter 18

The original and where it stands today

What is proven, what is my own account, and what the platform does now

What the sources prove

What is my own account

What I do not claim

I did not invent fair value. Benjamin Graham described the intrinsic value of a stock in the 1930s, and discounted cash flow is older than I am. What is mine is the product: the specific combination of models, the long public development and the decision to make this kind of analysis usable for private investors.

In recent years large financial websites have added automatic fair value figures of their own. I take that as confirmation that the idea was right. I cannot say and do not say that anyone copied anything. What I can say is simple: when you read Fair Value Calculator, this is the one that has carried the name in public since March 2016, and you can check every step of it.

Where the platform stands today

The single calculator of 2016 took two numbers. The platform of today values about 35,000 stocks worldwide with 26 valuation models and scores each company on up to 37 quality factors. Valuation and quality are two separate questions: whether a stock is cheap, and whether the business is good.

Browsing and valuing single stocks is free. The method is the same one this handbook teaches: separate price from value, insist on quality, diversify, and give it time.

Sources for Part IV

All sources were read again on 11 October 2026. The forum thread is in German.

[S1] Wertpapier-Forum, thread "Fair Value Calculator", page 1: launch post of 21 March 2016 and first criticism. https://www.wertpapier-forum.de/topic/48870-fair-value-calculator/

[S2] Wertpapier-Forum, page 2: backtests March to June 2016, stock split debate. https://www.wertpapier-forum.de/topic/48870-fair-value-calculator/page/2/

[S3] Wertpapier-Forum, page 3: helper calculators, tutorial video, market valuation, database 2016 and 2017. https://www.wertpapier-forum.de/topic/48870-fair-value-calculator/page/3/

[S4] Wertpapier-Forum, page 4: relaunch of 8 May 2019, detailed calculator of 4 December 2019. https://www.wertpapier-forum.de/topic/48870-fair-value-calculator/page/4/

[S5] Wertpapier-Forum, page 5: criticism of data and cyclical stocks, replies January to April 2020. https://www.wertpapier-forum.de/topic/48870-fair-value-calculator/page/5/

[S6] Wertpapier-Forum, page 6: 2020 to July 2026 (DCF and PEG, several models, free access, AI valuation, rebuild). https://www.wertpapier-forum.de/topic/48870-fair-value-calculator/page/6/

[S7] Wertpapier-Forum, page 7: feedback and corrections in July and August 2026. https://www.wertpapier-forum.de/topic/48870-fair-value-calculator/page/7/

[S8] Wertpapier-Forum, page 8: discussion up to 27 September 2026. https://www.wertpapier-forum.de/topic/48870-fair-value-calculator/page/8/

[S9] Klein, Peter (2020): "Die Fair Value Calculator Methode. Wahrer Wert schlägt den Markt", handbook, 77 pages (German). https://s0c1cccdcaae15a1c.jimcontent.com/download/version/1609693918/module/9220685476/name/ebook%202020.pdf

[S10] wikifolio "Fair Value Calculator" by Dr. Peter Klein, created on 30 March 2016. https://www.wikifolio.com/de/de/w/wf11224488

[S11] fairvalue-calculator.com: methodology, data and trust, current state. https://www.fairvalue-calculator.com/methodology

Appendix

Evidence map, glossary & references

Evidence map

EvidenceMain findingHow it informs the method
Low valuationCheap (low P/E, high book-to-market, high value-to-price) has historically earned higher returns.Use the fair-value gap and valuation multiples as the first filter.
QualityProfitability, financial strength and clean accounting improve the value universe.Avoid cheap-but-bad value traps; weight the Quality Score and AI-Quality.
Mean reversionExtreme pessimism and overreaction reverse over multi-year horizons.Hold long enough for price and value to meet (median ≈ 5 years).
DiversificationSingle-stock outcomes vary widely even when the average works.Build portfolios, not heroic one-stock bets.

Glossary — every term, in plain language

No finance degree needed. Every word you'll meet in the app and in this book, explained for beginners. Skim it once, then come back whenever a term trips you up.

The essentials

Fair value — a defensible estimate (shown as a range) of what a company is truly worth, built from its fundamentals — independent of today's mood-driven share price.

Intrinsic value — the same idea: the "real" worth a business should command based on what it earns and owns.

Value gap / Upside — fair value minus price, in percent. A big positive number means the stock looks cheap versus its worth.

Margin of safety — buying meaningfully below fair value, so you're protected if your estimate is a little off.

Mean reversion — over years, price and fundamental value tend to drift back toward each other. This is the engine that makes value investing work.

Quality Score — a 0–100 blend of profitability, growth, cash generation, balance-sheet strength and risk. It tells you how good the business is — separate from how cheap it is.

Evidence rating — how much clean, audited data backs an estimate (High = lots of solid data; Low = thin data, treat with care).

Bear / Base / Bull — a conservative, a central, and an optimistic fair-value estimate, so you see the realistic spread instead of one false-precise number.

Signal (Hold / Sell) — the app's simple rule derived from price versus fair value, your entry price, and the long-term trend.

MA250 — the average price over the last 250 trading days (≈ one year); a simple long-term trend line.

Market cap — share price × number of shares: the company's total value on the stock market.

Profitability & quality

Gross Profitability — gross profit ÷ total assets; how much raw profit the company squeezes from everything it owns — a hard-to-fake sign of a strong business.

Return on Assets (ROA) — net profit ÷ total assets; how efficiently the company turns its assets into profit.

Return on Equity (ROE) — net profit ÷ shareholders' equity; how much profit is earned on the owners' money.

Profit Margin — net profit ÷ revenue; how many cents of every sales dollar end up as profit.

Asset Turnover — revenue ÷ total assets; how much sales the company generates per dollar of assets.

Growth

Revenue growth (YoY) — sales versus the prior year; is the business actually expanding?

Δ (delta) — the "Δ" before a metric means change versus last year. ΔROA, ΔGross margin, ΔAsset turnover, ΔEBITDA margin rising = the fundamentals are improving.

Equity growth — how fast shareholders' equity (retained value) is compounding.

Asset growth (scored in reverse) — very fast asset growth often precedes weaker future returns, so a slower, disciplined grower can score better.

Cash & balance-sheet strength

OCF margin — operating cash flow ÷ revenue; the real cash (not just accounting profit) the core business produces.

FCF margin / FCF Yield — free cash flow (what's left after running and maintaining the business) ÷ revenue, or ÷ market value; the cash owners can actually use.

Accruals quality (OCF/NI) — operating cash flow versus reported profit. Profits backed by real cash (ratio near or above 1) are higher quality than paper profits.

Solvency (E/A) — equity ÷ assets; the share of the company funded by owners rather than debt. Higher = a stronger, safer balance sheet.

Debt-to-Equity — debt relative to equity; lower leverage means lower financial risk.

Altman Z-Score — a classic bankruptcy-risk score from several balance-sheet ratios; higher = financially safer.

Current ratio — short-term assets versus short-term bills: can the company cover the near term?

Cash / Assets — cash as a share of assets; a liquidity cushion for tough times or opportunities.

Piotroski F-Score — a 0–9 checklist of fundamental health (profitability, cash, leverage, efficiency). Higher is stronger.

Momentum & risk

Price momentum (3m / 6m / 12-1m) — the recent price trend; historically, stocks trending up have tended to keep outperforming short-term.

52-week high proximity — how close the price is to its one-year high; near the high often signals strength rather than being over-extended.

Realized volatility — how much the price swings; calmer stocks have historically delivered better risk-adjusted returns.

Beta — sensitivity to overall market moves; low-beta stocks have historically rewarded patient investors.

Net share issuance / buybacks — fewer shares (buybacks) lift per-share value; issuing many new shares dilutes existing owners.

Valuation multiples

P/E — price ÷ earnings; what you pay per dollar of annual profit. P/B — price ÷ book value (net assets). P/S — price ÷ sales. EV/EBITDA — company value including debt ÷ operating earnings, a debt-aware multiple. For all of these, lower usually means cheaper.

Dividend yield — the annual dividend as a percentage of the share price.

Terms you'll see in the app

Watchlist — your saved stocks, tracked with live Hold/Sell signals and performance since you added them.

Diversification — spreading across sectors, regions, company size and correlation so a single bad bet can't sink your portfolio.

Market Valuation & Cash Range — whether the overall market looks cheap, fair or expensive right now, and a suggested cash buffer.

Penny / micro-cap guard — extra caution flags on very small, thinly-traded stocks where data and prices are less reliable.

ESG — Environmental, Social & Governance: how responsibly a company treats the planet, its people, and how it is run.

References

  1. Basu, S. (1983). The relationship between earnings' yield, market value and return for NYSE common stocks. Journal of Financial Economics.
  2. Fama, E. F., & French, K. R. (1992). The cross-section of expected stock returns. The Journal of Finance, 47(2), 427–465.
  3. Lakonishok, J., Shleifer, A., & Vishny, R. W. (1994). Contrarian investment, extrapolation, and risk. The Journal of Finance, 49(5), 1541–1578.
  4. De Bondt, W. F. M., & Thaler, R. (1985). Does the stock market overreact? The Journal of Finance, 40(3), 793–805.
  5. Piotroski, J. D. (2000). Value investing: the use of historical financial statement information to separate winners from losers. Journal of Accounting Research, 38(Suppl.), 1–41.
  6. Frankel, R., & Lee, C. M. C. (1998). Accounting valuation, market expectation, and cross-sectional stock returns. Journal of Accounting and Economics, 25(3), 283–319.
  7. Novy-Marx, R. (2013). The other side of value: the gross profitability premium. Journal of Financial Economics, 108(1), 1–28.
  8. Asness, C. S., Frazzini, A., & Pedersen, L. H. (2019). Quality minus junk. Review of Accounting Studies, 24(1), 34–112.
  9. Fama, E. F., & French, K. R. (2015). A five-factor asset pricing model. Journal of Financial Economics, 116(1), 1–22.
  10. Jegadeesh, N., & Titman, S. (1993). Returns to buying winners and selling losers. The Journal of Finance, 48(1), 65–91.
  11. George, T. J., & Hwang, C.-Y. (2004). The 52-week high and momentum investing. The Journal of Finance, 59(5), 2145–2176.
  12. Ang, A., Hodrick, R. J., Xing, Y., & Zhang, X. (2006). The cross-section of volatility and expected returns. The Journal of Finance, 61(1), 259–299.
  13. Frazzini, A., & Pedersen, L. H. (2014). Betting against beta. Journal of Financial Economics, 111(1), 1–25.
  14. Titman, S., Wei, K. C. J., & Xie, F. (2004). Capital investments and stock returns. Journal of Financial and Quantitative Analysis, 39(4), 677–700.
  15. Sloan, R. G. (1996). Do stock prices fully reflect information in accruals and cash flows about future earnings? The Accounting Review, 71(3), 289–315.
  16. Beneish, M. D. (1999). The detection of earnings manipulation. Financial Analysts Journal, 55(5), 24–36.
  17. Altman, E. I. (1968). Financial ratios, discriminant analysis and the prediction of corporate bankruptcy. The Journal of Finance, 23(4), 589–609.
  18. Graham, B., & Dodd, D. L. (1934). Security Analysis. New York: McGraw-Hill. — and Graham, B. (1949). The Intelligent Investor.
  19. Sharpe, W. F. (1991). The arithmetic of active management. Financial Analysts Journal, 47(1), 7–9.
  20. Carhart, M. M. (1997). On persistence in mutual fund performance. The Journal of Finance, 52(1), 57–82.
  21. Kahneman, D., & Tversky, A. (1979). Prospect theory: an analysis of decision under risk. Econometrica, 47(2), 263–291.
  22. Harvey, C. R., Liu, Y., & Zhu, H. (2016). …and the cross-section of expected returns. The Review of Financial Studies, 29(1), 5–68.
  23. McLean, R. D., & Pontiff, J. (2016). Does academic research destroy stock return predictability? The Journal of Finance, 71(1), 5–32.
  24. Bailey, D. H., Borwein, J., López de Prado, M., & Zhu, Q. J. (2014). Pseudo-mathematics and financial charlatanism: the effects of backtest overfitting. Notices of the AMS, 61(5).
  25. Hou, K., Xue, C., & Zhang, L. (2020). Replicating anomalies. The Review of Financial Studies, 33(5), 2019–2133.
  26. Fama, E. F. (1998). Market efficiency, long-term returns, and behavioral finance. Journal of Financial Economics, 49(3), 283–306.
  27. [S1] Fairvalue Calculator internal backtests & evidence (2005–Aug 2025 samples; 100-stock convergence study since 2015); S&P Dow Jones Indices SPIVA scorecards (active-vs-passive). Internal results are hypothetical and educational.

Risk & compliance

This handbook is educational research only and is not financial advice, investment advice, or a recommendation to buy or sell any security. Examples, backtests, internal samples and statistics are historical or hypothetical and may not repeat. Value can underperform for years; cheap stocks can be value traps; concentration can destroy a good average. You are responsible for your own decisions, taxes, costs, risk tolerance and horizon. Past performance does not guarantee future results.

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Fairvalue Calculator · The Fair Value Playbook · 2026 edition · fairvalue-calculator.com
Educational research only — not financial advice.