Kelly criterion calculator
Size your stake to your edge — full, half or quarter Kelly.
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.
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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
- 1Enter the odds and probability. Type the decimal odds and your estimated win chance.
- 2Add your bankroll. Enter the total bankroll you're staking from.
- 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.
Embed it on your site
Paste this where you want the kelly stake calculator to appear. The script auto-mounts every widget on the page; swap data-or-theme for light, dark or transparent.
<div data-or-widget="kelly" data-or-theme="light"></div>
<script src="https://oddsrelay.io/widgets/oddsrelay-widgets.js" async></script>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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