Margin of Safety: What It Is and How to Use It

By Peter · 28 Sept 2026

Every valuation method on this site, the Graham Number, intrinsic value, produces an estimate. Not a fact. Margin of safety is the idea Graham built to deal with that honestly: since any estimate can be wrong, only buy when the price is low enough to absorb being wrong.

It's less a formula than a habit of mind, though it does have a simple calculation behind it.

The Margin of Safety Formula

Margin of Safety = (Intrinsic Value − Market Price) ÷ Intrinsic Value

You take your estimate of what a company is actually worth, subtract what the market is currently charging for it, and express the gap as a percentage of that estimate.

Worked Example

Say your intrinsic value calculation puts a company at €50 per share, and it's currently trading at €35.

Margin of Safety = (€50 − €35) ÷ €50 = 30%

You're being offered the chance to buy something you believe is worth €50 for €35, a 30% discount to your own estimate.

Why This Exists

The formula itself isn't the interesting part. What matters is why Graham insisted on it.

Every input that goes into an intrinsic value calculation, the growth rate, the discount rate, next year's earnings, is a guess about the future. Reasonable guesses, built on real numbers, but guesses all the same. If you buy a stock at exactly what you calculate it's worth, you're implicitly betting that your estimate is correct. Any error in your favor barely matters; any error against you means you overpaid.

A margin of safety is a buffer against being wrong. Buy at a large enough discount to your estimate, and even a meaningfully flawed calculation can still leave you with a reasonable outcome. It shifts the question from "is my estimate right?" (which you can't know) to "is the price low enough to tolerate my estimate being somewhat wrong?" (which is a much more answerable question).

How Big Should the Margin Be?

Graham himself favored large margins, often 30 to 50%, particularly for less predictable businesses. There's no single correct number, but a few things reasonably push it up or down.

A more predictable business, stable earnings, a long track record, limited competitive threat, can justify a smaller margin, since there's less that's likely to surprise you. A less predictable one, a newer company, a cyclical industry, a business facing real competitive or technological risk, deserves a wider margin, since the range of things that could go wrong is larger. The size of the margin you demand is really a statement about how much confidence you actually have in your own estimate, not a fixed rule that applies the same way to every company.

Where This Can Mislead You

A large margin of safety doesn't protect you from a bad estimate, only from a moderately wrong one. If your growth rate or earnings assumptions are badly off, no discount is guaranteed to be large enough. Margin of safety is a buffer, not a guarantee, and it works best paired with a genuinely conservative intrinsic value calculation in the first place rather than as a substitute for one.

It's easy to talk yourself into a discount that isn't really there. If the intrinsic value estimate itself is optimistic, say the growth rate is too high, then even a stock trading at a 30% "discount" to that inflated number might not actually be cheap. The margin of safety is only as trustworthy as the estimate it's measured against.

A wide margin can also mean the market knows something you don't. A stock trading well below any reasonable estimate of its value is sometimes a genuine opportunity, and sometimes a sign the business has a real problem the market has already priced in. A large gap is a reason to look closer, not a reason to buy automatically.

FAQ

What is a good margin of safety percentage?

There's no single number that applies everywhere. Graham generally looked for 30 to 50%, wider for less predictable businesses and narrower for stable, well-understood ones. Treat it as a reflection of how confident you are in your own estimate rather than a fixed rule.

Who came up with the margin of safety concept?

Benjamin Graham, widely regarded as the father of value investing, introduced it in his books Security Analysis (1934, with David Dodd) and The Intelligent Investor (1949). Warren Buffett, who studied under Graham, has credited it as one of the most important ideas he learned from him.

Is margin of safety the same thing as intrinsic value?

No. Intrinsic value is your estimate of what a company is actually worth. Margin of safety is the gap between that estimate and the current market price, expressed as a percentage. You need an intrinsic value figure before you can calculate a margin of safety at all.

Does a large margin of safety guarantee a profitable investment?

No. It reduces the damage from a moderately wrong estimate, but it can't protect you from a badly wrong one, and it says nothing about how long it might take the market to recognize the gap, if it ever does. It's risk reduction, not a guarantee.

How is margin of safety different from a stop-loss?

A stop-loss is a price-based exit rule set after you buy, meant to limit losses if a stock falls. Margin of safety is applied before you buy, as a discount to your own estimate of value. One is about limiting downside on a position you already hold; the other is about deciding what to pay for a position in the first place.