Kelly Criterion Calculator
Enter your bankroll, the odds you can get and your own estimate of the win chance. It shows your edge and expected value, and the Kelly stake. It runs in your browser and nothing is sent anywhere.
Your bet
Result
How the Kelly criterion works
Stake = bankroll × Kelly share × your fraction
Edge = win chance − break-even chance (break-even = 1 ÷ decimal odds)
EV per $1 = win chance × decimal odds − 1
Kelly sizes a bet by how big your edge is: the larger the edge, the larger the share of your bankroll, and no edge means no bet. Example: at +110 (2.10) with a 55% win chance, the break-even chance is 47.6%, the edge is 7.4 points, EV is +15.5% per $1, and full Kelly is 14.1% of the bankroll.
The formula assumes your win chance is exactly right. It never is, and an estimate that is too high leads full Kelly to overbet badly. That is why many bettors use half, quarter or even tenth Kelly, which gives up some growth for much smaller swings. This page defaults to quarter Kelly.
Kelly is for one bet at a time. It does not model several bets at once, related bets, pushes, or a bet limit. It is a staking rule, not a prediction, and does not guarantee a profit.
Common questions
What is the Kelly criterion?
A formula for the share of your bankroll to stake on a bet with a positive edge. It is (decimal odds × win chance − 1) ÷ (decimal odds − 1). If the result is zero or negative, there is no positive edge and the formula says not to bet.
Why do people use fractional Kelly?
Full Kelly assumes your win chance is exactly right. If your estimate is too high, full Kelly overbets and the swings are large. Half or quarter Kelly stakes much less and is far less sensitive to estimation errors.
Where do I get my win probability?
Kelly needs your own estimate of the true chance. A common starting point is the fair probability after removing the vig from a sharp market, which a no-vig calculator can give you. It is only an estimate.
Does Kelly guarantee a profit?
No. It is a staking rule that depends on your estimate being accurate. Even with a real edge, single bets and whole stretches of bets can lose.
More free tools
- Devig TerminalRemove the vig and find a fair win chance.
- My Bets → BankrollTrack your bankroll and set spending limits.
- Odds ConverterSwitch between American, decimal and fractional odds.
- Parlay CalculatorCombine several legs into one price and payout.
For information only, not betting advice. Estimates are not guarantees. Never bet more than you can afford to lose. Only wager where legal and if you meet the age requirement. If gambling is a problem, call or text 1-800-GAMBLER (1-800-426-2537).