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Kelly criterion calculator

A stake-sizing formula: given your own probability estimate and the price, how much of a bankroll does Kelly suggest?

Suggested stake
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Share of bankroll
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Expected value at your estimate
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Responsible staking: Kelly is only as good as your probability estimate, and estimates are usually too confident. Most people who use it bet a fraction (a quarter or less), cap any single bet, and never stake money they need. If betting stops being fun, call 1-800-GAMBLER.

What Kelly does (and doesn't) do

The Kelly criterion sizes a stake from the gap between your estimated chance and the chance the price implies. If your estimate is not above the implied probability, Kelly says stake nothing. It assumes your estimate is right, which it rarely is exactly; overestimating your edge with full Kelly leads to big swings, so fractional Kelly is the usual choice.

Read bankroll basics and responsible play before you size anything.

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