Kelly Criterion Sports Calculator
Get the right stake for your edge and bankroll — full, half, quarter.
How to Use This Calculator
- Tap to pick your odds format (Decimal, Fractional, or American)
- Type in the odds for your bet
- Add your own guess for the chance of winning (as a percentage)
- Pop in your total bankroll
- Get the Kelly fraction, your suggested stake, and the half/quarter Kelly options too
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
So what exactly is the Kelly Criterion?
It’s a math formula that works out the best bet size to grow your bankroll as much as possible over the long run, while keeping you safe from going bust.
Should I just bet the full Kelly amount every time?
Most seasoned bettors stick to fractional Kelly (half or quarter) to keep the ups and downs smaller. Even with a real edge, full Kelly can give you some wild swings.
What does it mean if Kelly comes back negative?
A negative Kelly number is telling you the bet has negative expected value. Skip it, because over time it would just cost you money.
How spot-on does my probability guess need to be?
Kelly reacts strongly to your probability input. If you overrate your edge you’ll bet too big, and that’s exactly why fractional Kelly is handy as a safety cushion.