What the Kelly criterion is
The Kelly criterion is a formula for sizing bets. It works out the share of your bankroll that grows it fastest over time, based on the odds and your edge. With no edge, it says bet nothing.
Kelly criterion calculator
Enter the odds, how often you think the bet wins and your bankroll. See how much the Kelly criterion says to stake, from full Kelly down to a tenth.
Suggested stake$20.91
Share of bankroll2.09%
Full Kelly8.36%
Your edge9.20%
For information only. Results use the odds you enter and don't include any sportsbook rules or limits.
How it works
Kelly criterion calculator: the basics
The formula
Kelly % = (b × p − q) ÷ b, where b is the decimal odds minus 1, p is your win chance and q is 1 − p. At +110 with a 52% win chance, full Kelly is 8.4% of your bankroll.
Why most bettors use fractional Kelly
Full Kelly assumes your win chance is exactly right, and it leads to big swings. Half or quarter Kelly gives up a little growth for much smaller drawdowns, and protects you if you overestimate your edge.
Kelly vs flat units
Many cappers stake flat units, like 1% per bet, because it's simple and easy to follow. Kelly suits bettors with a reliable way to estimate their edge on each bet.
Related guides: What is a unit in sports betting?
Terms used here: Kelly criterion · Edge · Bankroll · Full glossary
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FAQ
Kelly criterion calculator questions
How do I calculate the Kelly criterion?
Kelly % = (b × p − q) ÷ b. b is the decimal odds minus 1, p is your win probability and q is the chance of losing (1 − p).
What does a negative Kelly mean?
It means you have no edge at those odds: your win chance is below the break-even rate. Kelly says don't bet.
Should I use full Kelly?
Most bettors don't. Full Kelly is very aggressive and punishes you heavily if your win chance estimate is too high. Half or quarter Kelly is far more common.
Where do I get my win probability?
From your own model, or from no-vig fair odds at a sharp sportsbook. Kelly is only as good as that estimate.