Kelly criterion calculator: how much to bet

The Kelly criterion sizes a bet in proportion to its edge: the bigger the advantage, the larger the share of your bankroll. Enter the bankroll, the odds and the true win probability (or the fair odds): the calculator shows the full-Kelly share and the stake for full, half or quarter Kelly. With no edge, Kelly says not to bet.

Odds format
True chance as
%
Kelly fraction
Suggested stake$34.37
Share of bankroll3.44%
Full Kelly share6.87%

Want to keep a record of your bets and your real profit? Save them in the free Bet Tracker

How to use the calculator

  1. 1

    Enter your bankroll

    The money set aside for betting, not your savings.

  2. 2

    Enter odds and true chance

    The price offered and the fair odds or the win probability you estimate.

  3. 3

    Choose the Kelly fraction

    Full Kelly grows the bankroll fastest but swings hard; half or quarter Kelly is what most bettors use.

Worked example

Bankroll $1,000, odds +110 (2.10), true chance 51.22% (fair -105). Full Kelly = (1.10 x 0.5122 - 0.4878) / 1.10 = 6.88% of the bankroll, a $68.75 stake. Half Kelly bets $34.38, quarter Kelly $17.19.

Frequently asked questions

What is the Kelly criterion?

A formula published by John Kelly in 1956 that gives the stake maximizing the long-run growth of a bankroll, given the odds and the probability of winning.

Why use half or quarter Kelly?

Full Kelly assumes your probability is exactly right. Estimates never are, and full Kelly on an overestimated edge overbets. Fractional Kelly keeps most of the growth with far smaller swings.

What if the calculator says no edge?

The odds are at or below the fair price, so any stake has negative or zero expected value. Kelly's answer is to bet nothing.

Should I recalculate the stake after every bet?

Yes, Kelly is a share of the current bankroll: it grows after wins and shrinks after losses, which is what protects you from going broke.

Can I use Kelly for parlays?

Yes, with the parlay's total odds and its true probability (the product of the legs' probabilities). The stakes come out small, because parlays win rarely.

By the NinjaBet Editorial Team Updated on September 28, 2026

Bets with an edge, sized for you

ValueBet finds positive-EV bets live and suggests the Kelly stake for your bankroll on every one.

Already a member? Log in