Size the bet to the edge
Kelly Criterion Calculator
Enter the odds and your estimated win probability to see your edge and the Kelly stake.
Only as good as your probability estimate. Not financial advice.
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Guides that go with this calculator.
FAQ
Frequently asked questions
What is the Kelly criterion?
A formula for sizing bets when you believe you have an edge: stake = (b × p − q) ÷ b, where b is decimal odds − 1, p your win probability and q = 1 − p. At even money (2.00) with a 55% chance, full Kelly is 10.00% of your bankroll — $100.00 of $1,000.
Why do people use half Kelly?
Full Kelly is very aggressive and your probability estimate is never perfect. Half Kelly bets half as much ($50.00 in the example) for much smaller swings.
What if Kelly is negative?
It means you have no edge at those odds, so Kelly says don’t bet. At −110 with a 50% chance the edge is -4.55% and full Kelly is -5.00%.
Where does my probability come from?
From your own model or judgment — the calculator cannot tell you if it is right. If your estimate is too high, Kelly will tell you to over-bet.
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