Kelly Criterion Calculator
Calculate the mathematically optimal percentage of your bankroll to stake on a match to maximize long-term growth.
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Understanding Kelly Criterion Math
The Kelly Criterion is a formula used in investment and sports betting to determine the optimal size of a series of bets. In sports, it guides you to stake more when your edge over the market is large, and less when the edge is thin, protecting your bankroll from depletion.
What is the Kelly Criterion formula?
The Kelly Criterion formula is: f* = (b*p - q) / b. Where f* is the fraction of the bankroll to bet, b is the decimal odds minus 1, p is the probability of winning, and q is the probability of losing (1 - p).
Why should I use Fractional Kelly (Half or Quarter Kelly)?
Full Kelly maximizes long-term logarithmic growth but causes extreme short-term volatility and risk of ruin if your probability estimation is slightly off. Fractional Kelly (like Half Kelly at 0.5x or Quarter Kelly at 0.25x) provides a safer buffer and smoother bankroll growth.