Fractional Kelly Criterion Calculator
Explore what the Kelly Criterion implies for a given scenario. Enter a reference unit base, the market odds, and a model win probability to see the fraction the formula returns for those inputs. The output is a hypothetical illustration, not a recommendation, and it is only ever as reliable as the probability you supply.
Position-Sizing Calibrator
Enter a projection's model win probability and odds. We show the model-market difference and the fractional-Kelly percentage the formula returns for those inputs — capped so no single scenario exceeds 5% of your reference unit base. This is a research tool illustrating a hypothetical scenario, not investment advice or a recommendation to act.
Your inputs
Illustrative allocation range
EdgeSlate is a research and analytics product. This calculator holds no funds, and is not investment advice or a promise of outcomes. 21+. If sports-related risk creates stress or harm, pause and seek qualified support resources. 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.