Margin of Safety Calculator
The single most important rule in value investing: never pay full price for fair value.
Margin of Safety
What Is Margin of Safety?
Margin of safety is the gap between what a business is actually worth (its intrinsic value) and what you pay for it. Benjamin Graham considered it the central concept of intelligent investing: because no valuation estimate is perfectly precise, buying at a meaningful discount to your estimate protects you against errors in your own analysis, unexpected bad news, or general market pessimism.
The formula is: Margin of Safety % = (Intrinsic Value − Market Price) ÷ Intrinsic Value × 100. A positive number means the stock is trading below your estimate of fair value — the larger the number, the bigger your cushion. A negative number means you'd be paying more than your own estimate of what the business is worth.
How Much Margin of Safety Is Enough?
There's no universal answer, but common value investing convention suggests a 20–30% margin of safety for stable, well-understood businesses, and 50% or more for smaller, less predictable, or more cyclical companies where the intrinsic value estimate itself carries more uncertainty. Warren Buffett has described wanting to buy dollar bills for fifty cents — an intentionally large cushion.
Where Does the Intrinsic Value Number Come From?
This calculator doesn't estimate intrinsic value for you — that's the hard, judgment-driven part of value investing. You'll need to arrive at your own estimate first, using a method like our Graham Number Calculator or DCF Calculator, or your own independent research and reasoning about the business.
Worked Example
Suppose your own analysis puts the intrinsic value of a share at €50 and the share trades at €38. The margin of safety is (50 − 38) ÷ 50 × 100 = 24%. If the price falls to €30, the margin grows to 40%. If the price rises to €55, the margin becomes −10%: you would be paying more than your own estimate of what the business is worth.
It also helps to work backwards. To find the highest price that still gives you the margin you want, multiply your value estimate by (1 − margin). For a 30% margin on a €50 estimate, the maximum price is 50 × 0.70 = €35.
| Intrinsic value | Margin wanted | Highest price to pay |
|---|---|---|
| €50 | 20% | €40.00 |
| €50 | 30% | €35.00 |
| €50 | 50% | €25.00 |
Use a Cautious Value Estimate
The margin is only as good as the value it is measured from. If your estimate is optimistic, a large margin can be an illusion. A sensible habit is to calculate intrinsic value under a cautious set of assumptions, for example lower growth and a higher required return, and measure the margin from that figure. The article Margin of Safety: What Life at Sea Taught Me About Investing works through a full example with three different views of the same company.
Frequently Asked Questions
Why not just buy at exactly fair value?
Because your estimate of fair value is just that — an estimate. Future earnings, competitive dynamics, and interest rates are all uncertain. A margin of safety absorbs the error in your own analysis, which is inevitable no matter how careful you are.
Does a large margin of safety guarantee a good investment?
No. If your intrinsic value estimate itself is wrong — for example, because the business is deteriorating in ways you haven't accounted for — even a stock that looks "cheap" relative to that flawed estimate can still be a poor investment. Margin of safety protects against estimation error, not against a fundamentally wrong thesis.
Can margin of safety be negative?
Yes — this simply means the market price exceeds your intrinsic value estimate. Value investors generally avoid buying in this situation, viewing it as paying a premium rather than getting a discount.