Kelly Calculator

What is the Kelly Criterion?

The Kelly Criterion is a mathematical formula used to determine the optimal size of a series of bets. It maximizes long-term growth while minimizing the risk of ruin by calculating what percentage of your bankroll to wager based on your edge and odds.

This calculator helps you apply the Kelly formula to find the optimal bet size for any wager, ensuring you maximize growth while protecting your bankroll from catastrophic losses.

Enter Bet Details
Enter the Kelly multiplier (0.5 = conservative, 1.0 = full Kelly)
Enter the odds in American format (e.g., +150 or -110)
Enter your estimated win probability (0-100)
Enter your current bankroll amount
Results
Kelly Analysis
  • Expected Value: 0.00%
  • Fraction of Bankroll to Wager: 0.00%
  • Amount to Wager: $0.00
Please enter valid values for all fields.
How to Use This Calculator

The Kelly Calculator helps you determine the optimal bet size based on the Kelly Criterion, which maximizes long-term growth while minimizing risk of ruin.

  • Kelly Multiplier: Adjust this to be more conservative (0.5) or aggressive (1.0)
  • Odds: Enter the odds in American format (e.g., +150 or -110)
  • Win Probability: Enter your estimated probability of winning (0-100%)
  • Bankroll: Enter your current betting bankroll amount

This calculator will show you:

  • The expected value of your bet
  • The optimal fraction of your bankroll to wager
  • The exact amount to bet

Note: The Kelly Criterion assumes you can accurately estimate your win probability. Be conservative with your estimates to avoid over-betting.

Tips & Best Practices
  • Use fractional Kelly (0.25-0.5) to reduce volatility and risk of ruin.
  • Only use Kelly when you have a genuine edge - overestimating win probability is dangerous.
  • Never bet more than 5-10% of your bankroll on a single wager, even if Kelly suggests more.
  • Track your results to verify your probability estimates are accurate over time.