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Betting Calculators

Free tools for parlay payouts, EV, Kelly sizing, and more.

Kelly Criterion Calculator

Calculate optimal bet sizing based on your assessed edge and bankroll.

Full Kelly5.5%
Half Kelly2.8%
Quarter Kelly1.4%

Kelly Criterion is a mathematical model, not financial advice. Bet sizing depends on your personal risk tolerance and bankroll. 21+ only, where legal.

How it works

The Kelly formula is f* = (b x p - q) / b, where b is the net odds received (decimal odds minus 1), p is your win probability, and q is 1 - p. The result is the fraction of your bankroll to wager.

Full Kelly maximizes long-run growth rate mathematically, but it requires an accurate probability estimate and leads to large swings. Most sharp bettors use Half or Quarter Kelly to reduce variance. When f* is zero or negative, the math says you have no edge at this line.

Kelly Criterion is a mathematical model. Actual bet sizing depends on your personal risk tolerance and circumstances. For entertainment purposes only. Not financial advice. 21+ where available.