Trading Expectancy & Kelly Calculator
Turn your win rate and average win/loss into expectancy per trade, profit factor, and the Kelly position size your edge supports.
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About the Trading Expectancy & Kelly Calculator
Expectancy tells you the average dollar (or R) result you can expect from each trade once your edge plays out over many trades. The core formula is expectancy = win % × average win − loss % × average loss. Enter your win rate and average win/loss above to get expectancy per trade, expectancy in R, profit factor, and the Kelly fraction. Use it to confirm a strategy is profitable before scaling size, and to compare two systems on a like-for-like basis.
Frequently Asked Questions
How do you calculate trading expectancy?
Expectancy per trade = (win % × average win) − (loss % × average loss). With a 50% win rate, a $200 average win and a $100 average loss, expectancy is 0.5 × 200 − 0.5 × 100 = $50 per trade. A positive number means the strategy has an edge.
What is a good expectancy in trading?
Any positive expectancy means you make money on average over many trades. Expressed in R (expectancy divided by average loss), 0.2R to 0.5R is a solid, realistic edge. The higher and more consistent the expectancy, the faster your account compounds.
What is the Kelly fraction this calculator shows?
The Kelly fraction is the share of capital that maximizes long-term growth for your win rate and payoff ratio: f = win % − (loss % ÷ payoff), where payoff is average win ÷ average loss. Most traders use half-Kelly or less because full Kelly is very volatile.