Tools · free
Kelly Criterion Calculator
The growth-optimal position fraction from your edge. Enter your win rate and reward-to-risk — we'll show full, half, and quarter-Kelly (and warn you if the math says you have no edge).
Estimate only, not financial advice.
Run it on your real trades
SignalDeck computes all of this automatically from your journaled trades — R-multiple, expectancy, SQN, Kelly, drawdown. Free during beta.
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FAQ
What is the Kelly Criterion?
Kelly gives the bet size that maximizes long-run growth. For trading: Kelly % = W − (1 − W) / R, where W is win rate (decimal) and R is your average win divided by average loss. If it's zero or negative, the math says you have no edge — don't size up.
Why do traders use half-Kelly?
Full Kelly is the growth-optimal size but extremely volatile, and it's unforgiving if your win-rate/edge estimates are even slightly off. Most traders use half- or quarter-Kelly: you give up a little growth for a large reduction in drawdown and estimation risk.