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Kelly criterion calculator

How much should you stake on a value bet? Enter your odds, the fair odds (from our no-vig calculator or a BetTheDrop alert) and your bankroll.

The Kelly formula

Kelly % = (odds × p − 1) ÷ (odds − 1) where p = 1 ÷ fair odds

Kelly stakes a share of your bankroll proportional to your edge: the bigger the value, the bigger the stake; with no value, no bet. In theory it grows a bankroll faster than any other staking plan.

Why most bettors use a fraction of Kelly

Full Kelly assumes your fair odds are exactly right. They never are, and full Kelly swings hard: drops of half your bankroll are normal. Quarter or half Kelly gives up a little growth for much smaller swings, and a cap per bet (for example 5% of the bankroll) protects you from a bad estimate. Read flat betting vs Kelly.

Example

Odds 2.10, fair odds 1.97 (a 50.8% chance), bankroll 1,000. The edge is +6.6%, full Kelly is 6.0% of the bankroll, and quarter Kelly is 1.5%: a stake of 15.

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Frequently asked questions

Should I use full Kelly?

Rarely. Most professionals bet a quarter to a half of Kelly because their probability estimates are never perfect.

What if Kelly says zero?

Then there's no edge at that price: don't bet.

Does Kelly work with flat stakes?

They are alternatives. Flat stakes are simpler; Kelly sizes each bet by its edge. Both need value to make money in the long run.

Keep reading

Flat betting vs the Kelly criterionFlat stakes or the Kelly criterion? How each staking plan works, the maths, the swings to expect and a practical middle ground for value bettors.Read →Bankroll management for value bettingBankroll management for value bettors: how big a unit should be, what losing runs to expect, flat vs Kelly stakes and habits that protect you.Read →No-vig calculator: fair odds & EVStrip the bookmaker's margin to get the fair odds, the true probability and the expected value (EV) of your bet. Power and multiplicative methods, 2 or 3 outcomes.Read →Closing line value calculatorFree closing line value calculator: enter the odds you took and the closing odds, remove the margin and see your CLV against the fair close.Read →