Kelly Criterion Calculator

Determine the optimal stake size to maximize long-term growth of your bankroll

What is the Kelly Criterion?

The Kelly Criterion is a mathematical formula used to determine the optimal size of a series of bets to maximize the logarithm of wealth. In betting, it helps you determine what percentage of your bankroll you should stake on a bet with positive expected value.

The formula is: Kelly % = (bp - q) / b

Where:

  • b = the decimal odds - 1 (i.e., the profit if you win)
  • p = the probability of winning
  • q = the probability of losing (1 - p)

Many professional bettors use a "fractional Kelly" approach (e.g., Half Kelly or Quarter Kelly) to reduce variance and risk of ruin.

This is your assessment of the true probability of the outcome occurring.
Kelly Criterion Results
Bookmaker's Implied Probability:
Your Estimated Probability:
Edge:
Full Kelly Percentage:
Half Kelly (Recommended):
Quarter Kelly (Conservative):
Recommendation:
Bankroll Allocation
Your Bankroll:
Full Kelly Stake:
Half Kelly Stake (Recommended):
Quarter Kelly Stake (Conservative):