Warren Buffett's Investing Criteria, Explained

Short answer: Warren Buffett’s approach boils down to buying a wonderful business at a fair price rather than a fair business at a wonderful price. In practice that means running a company through four filters — is it inside your circle of competence, does it have a durable economic moat, does it sit on a fortress balance sheet, and can you buy it with a margin of safety? Clear all four and you have a candidate worth studying.

Those four filters are the pillars the Market Lens methodology scores. Each gets a sub-score from 0 to 10, and the four are blended with fixed weights into one 0–100 composite. Here’s what each one means — and how Market Lens actually measures it.

1. Circle of competence — do you understand it?

Before valuation, before ratios, ask a blunt question: can you explain how this company makes money in a sentence or two? If you can’t, you can’t judge whether it will still be making money in ten years — and that judgment is the whole game.

Buffett’s rule isn’t “only buy simple things.” It’s “know where the edge of your knowledge is, and don’t invest past it.” A payment network, a beverage brand, and a railroad are all understandable. A company whose profits depend on technology or regulation you can’t evaluate is not — for you. The circle can be small; it just has to have a clear boundary.

A computer can’t know what you understand, so Market Lens approximates this pillar with a sector and industry lookup: businesses whose type is easy to forecast (beverages, packaged foods, railroads, insurance) score high, and ones that are hard to forecast (biotech, semiconductors, fast-moving tech) score low. It rates how understandable the kind of business is — not your personal expertise.

2. Economic moat — will it stay good?

A great business today is only worth owning if it stays great. A moat is the durable competitive advantage that protects profits from competitors — a beloved brand, a network effect, high switching costs, or a structural cost advantage rivals can’t copy.

You can’t see a moat directly, but the financials leave fingerprints:

• High, steady return on invested capital (ROIC) — a strong sign a business earns more than its cost of capital year after year.
• Stable or expanding profit margins — pricing power that competition hasn’t eroded.
• Consistent revenue — demand that doesn’t evaporate in a downturn.

The Market Lens Moat score uses a handful of these fingerprints from the latest data: net profit margin, return on equity, gross margin, revenue growth, plus a few points for company size (market cap) as a proxy for an established position. ROIC is shown separately in the report as a quality check, but it is not an input to the Moat score.

3. Fortress balance sheet — can it survive a bad year?

The best businesses don’t just grow; they endure. A fortress balance sheet means the company can take a punch — a recession, a lost customer, a lawsuit — without being forced into a fire sale.

What Market Lens looks at here:

• Low debt relative to equity — leverage magnifies both gains and disasters.
• A healthy current ratio — enough near-term assets to cover near-term bills.
• Positive free cash flow and operating cash flow — the business funds itself instead of leaning on lenders.
• A positive profit margin — a small bonus for a company that is actually profitable.

Buffett’s preference for financially conservative companies isn’t timidity. It’s that survival is the precondition for compounding. You can’t win long-term if you’re wiped out short-term.

4. Margin of safety — is the price fair?

This is the idea Buffett took from his teacher Benjamin Graham, and it’s what separates investing from speculating. Margin of safety means only buying when the price sits comfortably below your estimate of the business’s worth — so that even if your assumptions are partly wrong, you haven’t overpaid.

If you estimate a business is worth about $100 a share and it trades at $96, there’s no cushion for error. At $65, there is. That gap is your protection. Many investors build their estimate of value with a discounted cash flow model and cross-check it against the P/E ratio and price-to-book.

Market Lens keeps its margin-of-safety score simpler and more transparent. Its intrinsic-value estimate is the average of two numbers: the Graham Number and a growth-adjusted “fair P/E” value (earnings per share × a fair P/E roughly equal to the growth rate, capped between 8× and 20×). For Technology, Communication Services, Healthcare, and Consumer Cyclical companies, the Graham Number is left out and the fair-P/E value is used alone. Margin of safety = (estimate − price) ÷ estimate. The DCF appears as its own separate panel — a second opinion, not an input to the score.

How the four filters work together

When Buffett thinks it through, the questions tend to come in order:

1. Understandable? If not, stop.
2. Durable moat? If not, its cheap price is probably justified.
3. Financially strong? If not, one bad year could end the story.
4. Priced with a cushion? If not, wait — a great business bought too dear is still a mediocre investment.

Notice that price comes last. Buffett’s insight is that a cheap bad business is usually just a bad business, while a great business paid for correctly can compound for decades.

Market Lens does not run the four as a pass/fail sequence. It blends them: Circle of Competence counts for 25%, Moat 30%, Financial Strength 25%, and Margin of Safety 20% of a 0–100 composite. That means a strong pillar can partly offset a weak one — which is exactly why the Stock Analyzer shows each pillar separately. The result is labeled Meets criteria, Watch, or Fails criteria: a checklist result, not a recommendation to buy or sell.

A worked example: how the composite is built

Here’s how the weighted blend turns four sub-scores into one number. Imagine a company earns these sub-scores (each on the 0–10 scale the app uses), and remember margin of safety is first clamped to a −50% to +50% range before it’s mapped onto 0–10:

Pillar	Sub-score (0–10)	Weight	Contribution
Circle of Competence	8	25%	8 × 0.25 = 2.00
Moat	9	30%	9 × 0.30 = 2.70
Financial Strength	7	25%	7 × 0.25 = 1.75
Margin of Safety	4	20%	4 × 0.20 = 0.80

Add the contributions: 2.00 + 2.70 + 1.75 + 0.80 = 7.25 out of 10, which scales to a composite near 73 out of 100. Notice what happened: the business scores beautifully on quality (circle, moat, strength) but only middling on price — the margin-of-safety sub-score of 4 drags the composite down. A great business with a thin cushion is still only a “Watch,” not a “Meets criteria.” That is the weighting doing its job: price discipline is baked in, not bolted on. The exact sub-score formulas live on the methodology page.

How to read the verdict label

Label	Roughly what it means	What it is not
Meets criteria	High composite and a positive margin of safety plus solid moat and financial-strength sub-scores	Not a “buy” signal
Watch	Strong on some pillars, short on others — often a good business without a price cushion	Not a “wait to buy” instruction
Fails criteria	Falls short on quality, strength, or price by the checklist’s rules	Not a “sell” or “avoid” call

Every label is a measurement against a rules-based checklist — educational output you interpret yourself, never a recommendation to trade.

A note on patience

The hardest part of Buffett’s method isn’t the analysis — it’s the waiting. Most companies fail at least one filter, and even the ones that pass may not offer a margin of safety at today’s price. The discipline is doing the homework, then sitting on your hands until the price is right. Doing nothing, most of the time, is the strategy working as intended.

Common mistakes applying Buffett’s criteria

• Letting a cheap price excuse a weak business. A low price on a company with no moat is usually a value trap, not a bargain. Quality comes before price for a reason.
• Confusing a familiar product with a circle of competence. Using a company’s product doesn’t mean you understand its economics, competition, and ten-year outlook. The circle is about judgment, not brand loyalty.
• Treating the Moat score as if it included ROIC. In Market Lens the Moat score is built from margins, return on equity, revenue growth, and company size. ROIC is shown separately as a quality check — a common point of confusion worth getting right.
• Reading a “Meets criteria” label as a buy signal. It’s a checklist result against fixed rules, full stop. It does not tell you to buy, and a high score with a thin margin of safety is exactly why price stays its own pillar.
• Skipping the margin of safety because the business is wonderful. A great business bought too dear is still a mediocre outcome. The cushion is the protection against your own forecasting errors.

Frequently asked questions

What are Warren Buffett’s four investing criteria?

They are four filters: a circle of competence (do you understand the business?), an economic moat (does it have a durable advantage?), a fortress balance sheet (can it survive a bad year?), and a margin of safety (is the price below your estimate of value?). Market Lens scores each on a 0–10 scale and blends them — 25% / 30% / 25% / 20% — into one 0–100 composite.

Does a high Buffett score mean I should buy the stock?

No. The score produces a checklist label — Meets criteria, Watch, or Fails criteria — that measures a company against fixed rules. It is educational research, not a recommendation to buy, sell, or hold anything.

What’s the difference between the Moat score and ROIC here?

The Moat score is built from net profit margin, return on equity, gross margin, revenue growth, and company size. ROIC is reported separately as its own quality metric and is not an input to the Moat score, even though a sustained high ROIC is a classic fingerprint of a moat.

Why does price count for only 20%?

Because Buffett’s core insight is that a wonderful business bought at a fair price beats a fair business bought cheap. Weighting the three quality pillars at 80% keeps the focus on business quality, while the 20% margin-of-safety pillar still makes sure an overpriced great company can’t score a clean “Meets criteria.” You can run the full blend yourself in the Warren Buffett stock screener.

Putting it together

Buffett’s criteria are four questions asked in order: Do I understand it? Does it have a moat? Is it built to last? Is the price fair? Score each honestly and you’ve replaced hunches with a repeatable process.

That’s precisely what Market Lens automates — read the exact scoring formulas on the methodology page, or run all four filters on a real company in the Stock Analyzer. If you want to see the whole process end to end, start with how to value a stock.

Market Lens is educational research, not investment advice. Every figure is an estimate from public data that may be delayed or incomplete.