Kelly criterion calculator
A staking formula that sizes a bet from the odds and your own estimate of the probability. The result depends entirely on that estimate.
Odds format
Kelly fraction
%
£
Enter the details above to see the result.
Returns include the stake; profit is return minus total stake. Nothing is sent anywhere.
The formula
Kelly fraction = (p × b − (1 − p)) ÷ b, where p is your probability and b the decimal odds minus one. It maximises long-run growth only if the probability estimate is right; most people use a half or quarter fraction to reduce swings. An estimate that is too high leads to stakes that are too large.
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Calculators show arithmetic on the numbers you enter. They do not predict results. 18+. BeGambleAware.org.