Margin of Safety Calculator

What is margin of safety?

Benjamin Graham defined margin of safety as the gap between your estimate of value and the price you pay, expressed as a percentage of value. It's not about precision — it's about humility. You can't perfectly forecast earnings, interest rates or competitive dynamics, but you can refuse to overpay. A wide margin of safety means the business can disappoint and you still win.

Why 20–30% is a common bar

Twenty to thirty percent has settled in as a practical default for modern public markets because:

• It absorbs model error. If your fair value is 15% too high, a 30% margin still leaves you with a meaningful discount.
• It respects opportunity cost. A 50% margin of safety rarely appears outside deep bear markets or distressed businesses; waiting for it means sitting in cash for years.
• It scales with uncertainty. Stable, predictable businesses justify a thinner bar; cyclical, indebted or fast-changing businesses need a wider one.

How it interacts with estimate error

The most dangerous mistake in valuation isn't overpaying — it's being wrong about your own estimate and not knowing it. The scenario table below the result shows what happens to your margin if fair value is 10% or 20% higher or lower than you think. If the margin collapses to single digits on a modestly lower fair value, your conviction is fragile — either widen your required margin or dig deeper into the inputs before committing capital.

Always remember: the margin of safety lives in the price you pay, not in the model you use. A 50% MoS from a sloppy model is worse than a 15% MoS from a rigorous one. For a more robust fair value, cross-check with the stock fair value calculator's three-model blend, or test what the market's growth assumptions imply using the reverse DCF calculator.

Worked example

You estimate a company's fair value at $100 per share and set a 25% target margin of safety. The stock trades at $72. The calculator says:

• Current MoS: 28% — you are just above your target.
• Rating: Adequate (20–30% band).
• Max buy price at 25% target: $75. Since the market price is $72, you pass the target.
• Scenario check: If your fair value was actually $90, the margin shrinks to 20% — still adequate, but not exciting. If fair value was $110, the margin rises to 35% — deep value. The table makes the uncertainty transparent.

Frequently asked questions

What is margin of safety in investing?

Margin of safety is the gap between your estimate of a stock's fair value and its current market price, expressed as a percentage of fair value. It was Benjamin Graham's central protection against uncertainty: a wide buffer means your analysis can be partly wrong and you can still come out ahead.

How is margin of safety calculated?

Margin of safety = (fair value − current price) ÷ fair value × 100. If your fair value is $100 and the stock trades at $75, your margin of safety is 25%. The calculator also converts a target margin back into a maximum buy price: max buy = fair value × (1 − target margin).

Why do investors commonly use 20–30%?

Twenty to thirty percent has become a rule of thumb because it absorbs a reasonable degree of estimation error without requiring the market to be comically cheap. Graham himself often aimed for 33–50% in the 1930s, when prices were lower; modern investors usually settle for a thinner but more common 20–30%.

What margin of safety should I use for uncertain businesses?

Wider. If the business is cyclical, has high debt, operates in a regulated industry or faces rapid technological change, demand 30–50% or more. If it sells staple products, has pricing power and a decades-long track record, a 15–20% buffer may be enough. The margin should reflect the confidence you have in your inputs.