Kelly Criterion Calculator
The Kelly Criterion gives the mathematically optimal fraction of your account to risk per trade for long-term growth. Enter your win rate and average win/loss — it also shows the safer half-Kelly most traders actually use. Free, no signup.
Use your real numbers from your trade history. Garbage in, garbage out — Kelly is only as good as the win rate and averages you feed it.
Optimal sizing
Full Kelly is mathematically optimal but punishingly volatile — a normal losing streak can cut your account in half. Most pros use half Kelly for far smoother equity at ~75% of the growth.
Kelly needs your true win rate and averages. Pulling those from memory is how traders fool themselves — pull them from your data instead.
Get your real win rate & averages free →The formula
where p is your win probability, q = 1 − p, and bis the payoff ratio (average win ÷ average loss). A 55% win rate at a 1.5:1 payoff gives f* = 0.55 − 0.45/1.5 = 0.25 — Kelly says risk 25% of your account. That's aggressive, which is exactly why half Kelly (12.5% here) is the practical choice.
Kelly is only as good as your inputs
Plug in an optimistic win rate and Kelly will happily tell you to over-bet your way to ruin. The whole thing hinges on knowing your true win rate and average win/loss — the numbers most traders guess and get wrong. Pull them from your actual trade history instead. TradeFlow Quantum computes them for you, per setup. Start a free 7-day trial — no card required →