Kelly Criterion Calculator
Calculate the optimal bet size to maximize your long-term bankroll growth
Kelly Criterion Calculator
Calculate the optimal bet size based on your bankroll and perceived edge
0 of 3 free calculations used today
Today0/3Your estimate of the real probability of the event occurring
Recommended: 25-50% to reduce volatility
💡 Tip: Use 1/4 Kelly (25%) to reduce volatility without sacrificing too much growth. Full Kelly can generate brutal swings in your bankroll.
What is the Kelly Criterion?
The Kelly Criterion is a mathematical formula developed by John L. Kelly Jr. in 1956. It calculates the optimal percentage of your bankroll to bet based on your perceived edge and the odds offered. It's designed to maximize long-term growth while minimizing the risk of ruin.
Kelly Formula
Kelly % = (bp - q) / b
Where: b = odds - 1, p = probability of winning, q = 1 - pReal Example
Odds 2.50, estimated 45% probability: b = 1.5, p = 0.45, q = 0.55. Kelly = (1.5 × 0.45 - 0.55) / 1.5 = 8.33% of bankroll. With €1,000 bankroll, optimal bet = €83.30.
Kelly Fractions
Maximum growth, but high volatility. Only for very confident estimates.
Good balance between growth and risk reduction.
Recommended. Significantly reduces variance with minimal growth sacrifice.
For a complete guide on risk management strategies with Kelly Criterion, check our step-by-step tutorial.
Important Warnings
- ⚠️Negative Kelly = no value. Don't bet if the formula gives negative result
- ⚠️Your probability estimates must be accurate; overconfidence destroys bankrolls
- ⚠️Kelly assumes unlimited bankroll divisibility; in practice use conservative fractions
Save your calculations automatically
Track all your Kelly bets with BetStratify. See which fraction gives you the best results in real-time.