CALCULATORS · KELLY

Kelly criterion calculator for position sizing

Enter your win rate and your average win against your average loss to get the mathematically optimal fraction — and the fraction a human can survive.

How much is too much?

Kelly is the size that grows an account fastest over infinite trades. It is also brutally volatile, assumes your inputs are exact, and full Kelly on slightly-wrong numbers is how accounts die. Most people trade a quarter to a half of it.

HOW IT WORKS

Four steps, in order

1

Enter the win rate you actually achieve.

2

Add your average win and average loss.

3

Read the full Kelly fraction.

4

Trade a half or a quarter of it.

Kelly fraction

f* = (b × p − q) ÷ b, b = avg win ÷ avg loss

Full Kelly
17.50%
Half Kelly
8.75%
Quarter Kelly
4.38%
Half Kelly on this account
$2,187.50

Frequent questions

Short, practical answers. Trade-offs explained, no advice framing.

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