Kelly Criterion Calculator: How Much to Stake
The Kelly criterion gives the fraction of your bankroll that maximizes long-run growth: (b × p − q) ÷ b, where b is the net odds, p your win chance and q is 1 − p. If the result is zero or negative, it says not to bet. Most people stake only a fraction of it.
Key facts
- The Kelly criterion maximizes the expected logarithm of wealth (Wikipedia, Kelly criterion).
- For a bet at net odds b with win probability p, the optimal fraction is (b × p − q) ÷ b with q = 1 − p.
- Fractional Kelly lowers volatility and the damage from overestimating p.
Kelly answers one question: given an edge, how much should you stake so your bankroll grows fastest over time without risking ruin? It also warns you off bets that have no edge. The catch is that it trusts your win chance completely, which is why the fractional versions are popular. It runs in your browser, sends nothing anywhere and forgets your numbers when you close the page.
Kelly criterion calculator
Turn on JavaScript to use the calculator. The worked example below shows the same math by hand.
What you enter and what you get
You enter
- Odds: American, decimal or fractional.
- Your win chance (%): Your own estimate.
- Bankroll ($): an amount in dollars.
- How much of Kelly?: Full Kelly swings a lot.
You get
- Suggested stake
- Full Kelly fraction
- Full Kelly stake
- Stake you chose
- Edge per $1 staked
- Expected growth per bet (log)
How the calculator works
- Net odds b = decimal odds − 1.
- Full Kelly fraction = (b × p − (1 − p)) ÷ b.
- If that is zero or less, there's no edge: no bet.
- Multiply by your chosen fraction and by your bankroll to get the stake.
A worked example
Even-money odds (+100), a 55% win chance, a $1,000 bankroll and half Kelly.
| Item | Result |
|---|---|
| Suggested stake | $50 |
| Full Kelly fraction | 10% |
| Full Kelly stake | $100 |
| Stake you chose | $50 |
| Edge per $1 staked | $0.10 |
| Expected growth per bet (log) | 0.375% |
What the calculator leaves out
- If your win chance is too high, Kelly stakes too much. Overbetting costs more than underbetting.
- It assumes you can bet any amount and that bets are independent.
- It says nothing about sportsbook limits or how quickly you can place bets.
How we checked it
Before it went on the page we checked it against cases worked by hand: +100 at 55% with a $1,000 bankroll has to give a $100 full Kelly stake, half Kelly has to halve it, and no edge has to give no bet. The calculator is also run against thousands of odd entries such as blanks, zeros and huge numbers, so a bad entry shows a plain prompt and never a wrong number. The worked example above comes from the same code the calculator runs.
At a sweepstakes sportsbook
At a sweepstakes sportsbook your bankroll is in coins whose redeemable value is set by the site's rules, so a Kelly stake in coins isn't a Kelly stake in dollars. Treat it as a way to size risk, and read the redemption rules. See Sweepstakes vs Social vs Real-Money Casinos.
Betting math is not betting advice. Only play with money you can afford to lose, and if gambling stops being fun, call or text 1-800-GAMBLER.
Frequently asked questions
Why use half Kelly?
Estimates are noisy. Half Kelly gives up a little growth for much smaller swings and protects against an overconfident win chance.
What does a negative Kelly mean?
Your estimate is below the break-even chance, so you have no edge. Kelly says to bet nothing.
Can I use Kelly for several bets at once?
This version is for one bet at a time. Overlapping bets need smaller stakes than single-bet Kelly suggests.
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Sign up freeSources
- Kelly criterion, Wikipedia (read 2026-10-05)
- Bankroll management, Wikipedia (read 2026-10-05)
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