Kelly Criterion Calculator
Estimate full, half and quarter Kelly stakes from your bankroll, decimal odds and personal estimate of the true winning probability.
The calculation is only as reliable as the probability estimate entered. An overly optimistic estimate can produce an unsuitable stake, so many bettors use fractional Kelly or choose not to bet.
Calculate a Kelly Stake
Use decimal odds and a probability estimate between 0% and 100%.
Your Kelly Results
Kelly Criterion Formula
At odds of 2.00 with an estimated 55% chance of winning, the full Kelly fraction is 10% of bankroll. Half Kelly would be 5% and quarter Kelly 2.5%.
The original Kelly work concerns maximising long-run logarithmic growth under specific assumptions. It does not provide the true probability of a sports result; that estimate must come from the user.
Why fractional Kelly is commonly considered
Full Kelly can produce aggressive stakes and substantial drawdowns, particularly when probability estimates are uncertain. Half or quarter Kelly reduces the suggested stake, but it cannot correct a poor probability estimate or guarantee profit.
Kelly Criterion FAQ
Why does the calculator recommend no bet?
The odds do not show a positive mathematical edge under the probability estimate entered. The Kelly fraction is zero or negative.
What probability should I enter?
Enter your best reasoned estimate of the true chance of winning, not the bookmaker’s implied probability. If you cannot justify a reliable estimate, the calculator should not be used to decide a stake.
Is full Kelly safe?
No staking method makes betting safe. Full Kelly can be volatile and is highly sensitive to estimation error.
Background source: J. L. Kelly Jr., A New Interpretation of Information Rate.
Important Disclaimer
BettingGuru SA calculators are provided for educational and informational purposes only. Results are mathematical estimates based on the values entered and do not guarantee winnings, profit, successful withdrawals or future betting outcomes.
Always check the latest operator terms, odds, bonus rules, wagering requirements, settlement rules and withdrawal conditions before depositing or placing a bet.
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