Kelly Criterion Calculator

Calculate mathematically optimal bet sizes based on your edge

Input Parameters

Bankroll ($)

Bet Odds (American): -110

Decimal: 1.909 · Implied: 52.4%

Your True Win Probability: 55%

1%50%99%

+2.6% Edge Detected

Your estimated probability (55%) exceeds the implied probability (52.4%) by 2.6 points.

Kelly Recommendations

Full Kelly

5.5%

$550

High variance — not recommended

Half Kelly

2.8%

$275

Recommended for most bettors

Quarter Kelly

1.4%

$138

Conservative — lowest drawdown

Kelly Formula

f* = (bp - q) / b

b (net odds) = 0.909

p (win prob) = 0.550

q (loss prob) = 0.450

f* (fraction) = 0.0550

Monte Carlo Simulation (100 bets at Quarter Kelly)

Bet 0Final: $11,193Bet 100

Understanding Kelly Criterion for Your Handicapping Business

Why Half Kelly?

Full Kelly maximizes long-term growth but creates extreme variance. A 50% drawdown is common. Half Kelly achieves 75% of the growth rate with dramatically lower risk of ruin. Most professional bettors use 1/4 to 1/2 Kelly.

Estimating True Probability

The hardest part of Kelly is knowing your true win probability. Use no-vig consensus lines from sharp books (Pinnacle) as a starting point. Your handicapping edge is the difference between your model's probability and the market's.

For Your Clients

Recommend your clients use Kelly sizing on your picks. If you provide a confidence rating with each pick, they can adjust the true probability input accordingly. This turns your picks into a systematic, bankroll-managed strategy.