Betting calculators
Size every bet, evaluate every price, convert every format. The same maths sharps run — built into clean, instant tools.
Kelly Criterion Calculator
Find the mathematically optimal stake for your — sized to your bankroll.
What is the ?
Kelly is a formula for the bet size that maximises long-term bankroll growth, given your edge. Bet too much and ruins you; too little and you leave growth on the table.
Why most pros use fractional Kelly
Full Kelly is aggressive and assumes your probability estimate is exact. Half or quarter Kelly dramatically reduces swings for only a small reduction in growth — far safer when your edge is an estimate.
Honest probability estimates
Kelly only works if your probability estimate is accurate. Overestimating your edge leads to overbetting, which can destroy your bankroll. When unsure, use Quarter Kelly or less. It's better to bet too little than too much.