Betting calculator
Kelly Criterion Calculator
Use this Kelly Criterion calculator to estimate a stake size based on your bankroll, the odds, your estimated probability and a fractional Kelly setting.
Enter your bankroll, odds and estimated chance
The calculator estimates the full Kelly stake and lets you reduce it using fractional Kelly.
Half Kelly suggests staking £50.00, which is 5.00% of a £1,000.00 bankroll.
What is the Kelly Criterion?
The Kelly Criterion is a staking formula that estimates how much of your bankroll to risk when you believe you have an edge. It compares the odds with your estimated probability of winning.
If the odds imply a lower probability than your own estimate, Kelly may suggest a stake. If there is no estimated edge, Kelly suggests no bet.
Kelly Criterion formula
Kelly fraction = (b × p − q) ÷ b
b = decimal odds − 1
p = your estimated probability
q = 1 − p
Why fractional Kelly is common
Full Kelly can be aggressive because it assumes your probability estimate is accurate. In real betting, estimates can be wrong, odds can move and outcomes are uncertain.
Many bettors use half Kelly, quarter Kelly or smaller fractions to reduce volatility.