Kelly Criterion Calculator

Optimal bet sizing for long-term bankroll growth

Kelly Calculator
Lower fractions reduce variance at the cost of slower growth
Recommended Bet

Enter your values and click Calculate

Understanding Kelly Criterion

The Formula
Kelly % = (bp - q) / b
  • b = Decimal odds - 1 (net odds)
  • p = Your probability of winning
  • q = Probability of losing (1 - p)
Why Use Fractional Kelly?

Full Kelly maximizes long-term growth but comes with high variance. Most professionals use 25-50% Kelly to:

  • Reduce drawdown risk
  • Account for probability estimation errors
  • Maintain emotional control
  • Handle correlated bets better

Bankroll Management Rules

1-3%
Standard Bet

Normal confidence level bets

3-5%
Strong Plays

High confidence edge

5%
Max Bet

Never exceed this

20+
Unit Buffer

Minimum bankroll in units

Common Bankroll Mistakes
  • Chasing losses with larger bets
  • Not tracking bets and results
  • Betting with money you can't lose
  • Increasing unit size after wins
  • Betting too many games at once
  • Ignoring closing line value