Kelly criterion calculator
The mathematically optimal risk per trade from win rate and payoff — and why to halve it.
Payoff ratio
1.50
Full Kelly
25.0%
of equity per trade
Half Kelly
12.5%
Suggested risk
5.0%
quarter Kelly, capped at 5%
How it's calculated
Payoff is average win divided by average loss. Kelly fraction is the win rate minus the loss rate divided by the payoff. Full Kelly maximises long-run growth but produces brutal drawdowns, so most traders use half or a quarter of it. A negative Kelly means the strategy has no edge and should not be traded at any size.
Everything runs in your browser — nothing is sent anywhere. Results are estimates; your broker's contract specification is the final word.
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