Optimal Bet Sizing Calculator

Calculate Kelly Criterion and compare bet sizing strategies for optimal bankroll growth.

Your total available bankroll.
Your expected advantage on the bet. This is (expected_return - 1) for the bet.
Decimal odds of the bet. Even money = 2.0, 3-to-1 = 4.0. This is the multiplier on a win.
Conservative = 1/4 Kelly, Moderate = 1/2 Kelly, Aggressive = Full Kelly.

Kelly Criterion Results

Win Probability (implied)
Full Kelly Bet
Half Kelly Bet
Quarter Kelly Bet
Recommended Bet (your risk level)

Strategy Comparison (per 100 bets)

StrategyBet Size% of BankrollExpected Growth RateRisk Level

Fixed Percentage Alternatives

1% of Bankroll
2% of Bankroll
5% of Bankroll
Flat Bet (1 unit = bankroll/100)
Formula:
Kelly fraction f* = (b×p - q) / b, where b = decimal_odds - 1, p = win probability, q = 1 - p
Win probability derived: p = (edge + 1) / odds (adjusted for the stated edge)
Expected growth rate G = p×ln(1 + f×b) + q×ln(1 - f)
Source: Kelly (1956) "A New Interpretation of Information Rate"; Thorp "Beat the Dealer"