Kelly Criterion Calculator
Calculate the optimal fraction of your bankroll to bet using the Kelly Criterion formula.
Inputs
Enter your estimated edge and payout to compute the optimal bet fraction.
Your estimated chance of winning this bet (0–100).
Dollars won per dollar risked (e.g. 2 = win $2 for every $1 bet).
$
If entered, shows the dollar amount to wager.
Kelly Fraction Result
—
of bankroll
Dollar amount to wager
Fill in the inputs and click Calculate to see your optimal bet fraction.
No edge — do not bet.
The Kelly fraction is zero or negative, meaning the expected value is not in your favor for these inputs.
Formula Breakdown
Win probability (p)
Loss probability (q = 1 − p)
Win/loss ratio (b)
Full Kelly f* = (bp − q) / b
Applied fraction multiplier
Adjusted Kelly
Expected value per unit
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Summary
Calculate the optimal fraction of your bankroll to bet using the Kelly Criterion formula.
How it works
- Enter your estimated probability of winning the bet (as a percentage).
- Enter the win/loss ratio — how many dollars you win for every dollar risked (e.g. 2 means you win $2 for every $1 bet).
- The calculator applies the Kelly formula: f* = (bp - q) / b, where b is the odds, p is win probability, and q is loss probability.
- The result shows the optimal fraction of your bankroll to commit to this bet.
- Use fractional Kelly (e.g. half-Kelly) to reduce variance while still growing your bankroll.
Use cases
- Sports betting bankroll management.
- Poker and casino game stake sizing.
- Stock or options position sizing for quantitative traders.
- Evaluating whether a bet or investment has a positive expected edge.
- Comparing multiple betting opportunities to allocate capital optimally.
- Teaching probability and risk concepts in finance or statistics courses.
Frequently Asked Questions
Last updated: 2026-07-23 ·
Reviewed by Nham Vu