Margin of safety, explained
Margin of safety is the single idea that separates investing from gambling. It's the gap between what a business is worth and what you pay for it — and the bigger that gap, the more room your estimate has to be wrong without costing you.
“Confronted with a challenge to distill the secret of sound investment into three words, we venture the motto: margin of safety.”
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The margin of safety formula
Start with fair value — a conservative estimate of what a share should sell for. The margin-of-safety price is simply that value with a discount applied:
Say a share is conservatively worth $100 and you demand a 50% margin of safety. Your buy-below price is $50. If it turns out to be worth only $80 — your growth estimate was too rosy — you still bought at a discount. That cushion is the entire point.
Read the other direction, margin of safety describes how cheap a current quote is: (fair value − price) ÷ fair value. A stock trading at $60 against $100 of value carries a 40% margin of safety.
How big should your margin be?
The discount should scale with uncertainty. A stable, predictable business with a decade of consistent returns might justify a 25–40% margin. A company whose future is harder to read demands 50% or more. The less sure you are, the larger the gap you insist on — you are buying protection against your own errors, not the company's.
This is also why quality comes first. A margin of safety on a weak business is a trap: the value you discounted from may itself be evaporating. Screening for quality before applying any discount keeps you from buying cheap things that deserve to be cheap.
From a number to a decision
A margin-of-safety price is only useful if you act on it. The cleanest way is to turn it into zones: a buy zone at or below your margin-of-safety price, a watch zone as the price approaches it, and a sell zone when the price runs rich relative to value. Decide the levels calmly, in advance, then let patience — not the daily chart — do the work.
Frequently asked questions
What is a margin of safety in investing?
A margin of safety is the gap between a conservative estimate of a share's fair value and the price you actually pay for it. Buying well below fair value gives your estimate room to be wrong and still leaves you protected. Benjamin Graham called margin of safety the three most important words in investing.
What is the margin of safety formula?
Margin of safety price = fair value × (1 − margin %). For example, with a fair value of $100 per share and a 50% margin of safety, your buy-below price is $50. As a percentage of an actual quote, margin of safety = (fair value − price) ÷ fair value.
How big should a margin of safety be?
It depends on how confident you are in the estimate. Stable, predictable businesses might justify a 25–40% discount; harder-to-forecast ones call for 50% or more. The less certain the future, the larger the margin you should demand. A common default in value investing is 50%.
Why does a margin of safety matter?
Every valuation rests on assumptions — growth, multiples, required return — and any of them can be wrong. A margin of safety absorbs those errors. It turns investing from a bet on being exactly right into a process that survives being somewhat wrong, which over time is what protects and compounds capital.
Is margin of safety the same as a stop-loss?
No. A stop-loss reacts to price after you buy. A margin of safety is set before you buy — it's the discount to fair value that makes the purchase sensible in the first place. One is risk management on the way out; the other is discipline on the way in.
See the margin on every company
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Get startedWonderfolio is an educational research tool. It applies publicly known value-investing formulas to public data. Nothing on this page or in the app is personalized investment advice or a recommendation to buy or sell any security.