Kelly Criterion Calculator

Find the bet size that maximizes long-run bankroll growth given an estimated edge. Fractional Kelly multipliers reduce variance and protect against probability-estimate error.

Inputs

Bankroll (USD)Total money set aside for betting.

Odds (American)Example: -110 for a standard line, +120 for an underdog.

Your estimated win probabilityYour honest estimate, 0 to 100.

Kelly multiplierFractional Kelly reduces variance and protects against estimation error.

Result

Recommended bet$25.00

As % of bankroll2.50%

Full Kelly bet (reference)$100.00

Expected growth per bet+0.219%

What this means

Real edge detected. We recommend 0.25x Kelly to account for the inherent uncertainty in any probability estimate.

Formula

kelly_fraction = (decimal_odds × win_probability − 1) ÷ (decimal_odds − 1)
recommended_bet = bankroll × kelly_fraction × kelly_multiplier

Position Sizing Under Uncertainty

Bankroll Management