Staking calculator
The Kelly criterion sizes bets in proportion to your edge. This calculator applies a fraction of Kelly, because full Kelly assumes your probability estimate is perfect — and it never is.
The formula
Full Kelly fraction = (odds × probability − 1) ÷ (odds − 1). The calculator multiplies that by your chosen fraction — 25–50% of Kelly is a common range for bettors who take estimation error seriously.
Why not full Kelly
- Estimation error: if your true edge is smaller than you think, full Kelly systematically overbets, and overbetting an edge is how bankrolls die even with positive EV.
- Variance: full Kelly routinely produces drawdowns most people cannot sit through without abandoning the strategy at the worst moment.
- Correlated exposure: Kelly assumes independent bets. Multiple open bets on related markets are not independent.
Staking for arbitrage is different
Arbitrage stakes are set by the odds themselves — use the arbitrage calculator for stake splits. Kelly applies to value bets, where you carry the variance; the probability input should come from the same estimate you used in the EV calculator. For how staking fits into overall money management, read the bankroll management guide.
A hard rule worth keeping: if a losing streak at your calculated stakes would push you to bet money you cannot afford to lose, the stakes are wrong regardless of the math. See our responsible gambling guide.