Kelly Criterion Calculator
Enter your win probability and win/loss ratio to get the Kelly percentage — the mathematically optimal fraction of your capital to risk per trade. Includes full Kelly, half Kelly, and quarter Kelly outputs.
Percentage of trades that win
Avg win ÷ avg loss
Full Kelly
32.50%
Risk this fraction of capital per trade
½ Kelly (recommended)
16.25%
Lower drawdown
¼ Kelly (conservative)
8.13%
Very stable equity
Formula
Kelly = W − (1−W) / RW = win rate, R = win/loss ratio
How it works
This kelly criterion calculator runs entirely in your browser — no data is sent to any server. Simply fill in the fields above and the result updates instantly. You can copy the output with the copy button provided.
Frequently Asked Questions
What is the Kelly Criterion?
The Kelly Criterion is a formula that determines the optimal fraction of your capital to bet on a positive expected value opportunity to maximize long-run growth rate.
What is Half Kelly?
Half Kelly means betting half the Kelly-recommended size. It reduces volatility significantly while capturing ~75% of the growth rate — popular among professional traders.
What if the Kelly result is negative?
A negative Kelly value means the edge is negative — you have no mathematical advantage and should not take the trade.