Kelly criterion calculator
The Kelly criterion stakes the share of your bankroll that maximises long-run growth. With a 55% chance at even money it is 10%; with no edge it is zero, and staking twice the Kelly amount grows the bankroll no faster than betting nothing at all.
How it works
- Kelly stake = (b × p - q) / b, where b = decimal odds - 1, p is your probability of winning and q = 1 - p.
- Expected growth per bet = p × ln(1 + b × f) + q × ln(1 - f) for a stake f of the bankroll. Full Kelly makes it largest: 0.50% per bet in the example.
- Half Kelly keeps 75% of that growth with far smaller swings, which is why many bettors use a fraction.
- Everything depends on your probability being right. An overestimated edge makes Kelly stakes too big, and too big a stake shrinks a bankroll on average.
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