Calculate Kelly Criterion
Optimal stake from edge and bankroll: full, half and quarter Kelly.
How to Use This Calculator
- Tap your odds format (Decimal, Fractional, or American)
- Drop in the odds for your bet
- Add your estimated win probability as a percentage
- Enter your full bankroll
- Get the Kelly fraction, the recommended stake, plus half and quarter Kelly options
Formula
Kelly Criterion Formula:
f* = (bp - q) / b
Where:
- f* = fraction of bankroll to wager
- b = decimal odds - 1 (net profit per dollar)
- p = probability of winning
- q = probability of losing (1 - p)
Expected Value = (p x b) - q
Frequently Asked Questions
What exactly is the Kelly Criterion?
It’s a math formula that pinpoints the ideal bet size to grow your bankroll as fast as possible over the long run while keeping you clear of going broke.
Is full Kelly always the move?
Most seasoned bettors dial it back to fractional Kelly (half or quarter) to smooth out the ride. Full Kelly can swing hard even when your edge is real.
What's a negative Kelly value telling me?
A negative Kelly value flags a bet with negative expected value. Skip it, because over time it’s a money loser.
How precise does my probability estimate have to be?
Kelly reacts sharply to your probability inputs. Overrate your edge and you’ll overbet, which is exactly why fractional Kelly exists as a built-in safety buffer.