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Kelly criterion calculator

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Size your stake to your edge — full, half or quarter Kelly.

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The Kelly criterion sizes a stake to your edge and bankroll. Enter the odds, your estimated win probability and your bankroll; the calculator returns the recommended stake and the full-Kelly fraction. Most bettors use a fraction of full Kelly to smooth out the swings.

What it does

  • Recommended stake and the full-Kelly fraction
  • Full, half and quarter Kelly options
  • A no-edge verdict when the bet isn't worth it
  • Pure client-side maths — your numbers stay with you

How to use it

  1. 1Enter the odds and probability. Type the decimal odds and your estimated win chance.
  2. 2Add your bankroll. Enter the total bankroll you're staking from.
  3. 3Choose a Kelly fraction. Full, half or quarter — then read off the recommended stake.

What powers this

This calculator runs entirely in your browser. There's no account, no API key and no feed — nothing you type leaves the page. The maths is the same commodity matched-betting and value arithmetic used across the industry, implemented carefully and unit-tested.

Questions

What is the Kelly criterion?
Kelly is a staking formula that sizes each bet to your edge: fraction = (odds × probability − 1) ÷ (odds − 1). It maximises the long-run compounding of a bankroll when your probability estimate is accurate.
Why use half or quarter Kelly?
Full Kelly is volatile and unforgiving of over-optimistic probabilities. Staking a fraction of full Kelly cuts the variance a lot while keeping most of the upside — which is why many bettors prefer it.
What if there's no edge?
If your probability times the odds is 1 or less, the Kelly fraction is zero or negative and the calculator recommends no bet.

18+ · Data product for licensed operators. Please gamble responsibly.

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