Fractional Kelly Criterion Calculator
Calculate your optimal position size using the Kelly Criterion. Simply input your reference unit base, the market odds, and your edge (model win probability) to determine the mathematically optimal position size.
Position-Sizing Calibrator
Enter a projection's model win probability and odds. We compute the edge and a disciplined, fractional-Kelly percentage allocation — capped so no single position risks more than 5% of your reference unit base. This is a research tool, not investment advice.
Your inputs
Recommended units
EdgeSlate is a research and analytics product. This calculator does no wagering, holds no funds, and is not investment advice or a promise of profit. 21+. If you or someone you know has a gambling problem, call 1-800-GAMBLER. Invest responsibly and never stake more than you can afford to lose.
What is the Kelly Criterion?
The Kelly Criterion is a mathematical formula used to determine the optimal size of a series of positions in order to maximize the logarithm of wealth. In probabilistic sports markets, it helps you manage your reference unit base by suggesting larger positions when you have a high edge, and smaller positions when your edge is low.
Why use "Fractional" Kelly?
Full Kelly is mathematically optimal for maximizing growth, but it is extremely volatile and assumes your edge calculations are perfectly accurate. Because sports models are inherently probabilistic and variance is high, disciplined practitioners almost universally use a "Fractional" Kelly approach (typically 1/4 or 1/2 Kelly). This significantly reduces variance and the risk of ruin while maintaining steady unit-base growth.
How to use this calculator
- Unit base: Enter your total dedicated research unit base.
- Odds: Enter the market odds for the position (e.g. -110 or +150).
- Win Probability: Enter the model's true probability of the position winning (this is where you need a model like EdgeSlate's).
- Risk Level: Choose your fractional multiplier. We recommend Conservative (1/4 Kelly) for most users.
Disclaimer: This calculator is for educational and research purposes only. It does not constitute financial advice or a recommendation to take any positions. Use within personal limits and never risk more than you can afford to lose.