Kelly Criterion Calculator — Optimal Bet Sizing
Find the mathematically optimal bet size to maximize long‑term bankroll growth. Enter your bankroll, win probability, and odds.
p = win probability, q = 1-p, b = decimal odds minus 1 (net profit per unit stake).
The result is the fraction of bankroll to wager. Full Kelly can be aggressive; many use fractional Kelly (e.g., 0.5).
📘 How to Use the Kelly Criterion Calculator
The total amount you have allocated for betting.
Your best estimate of the chance the bet wins.
Use format like -110, +150.
Use 1 for full Kelly, 0.5 for half-Kelly to reduce risk.
The tool shows the optimal bet amount and the fraction of bankroll to wager.
📈 Understanding the Kelly Criterion
- Maximizes long-term growth: Kelly balances risk and reward to grow your bankroll fastest.
- Avoids overbetting: If the edge is small, Kelly recommends a smaller bet.
- Fractional Kelly: Using a fraction (e.g., half) reduces volatility while still maintaining positive growth.
- Requires accurate probability estimates: Your win probability must be realistic; overestimating leads to overbetting.
🎯 Kelly Strategy & Tips
Combine with EV
Start with Fractional Kelly
Re‑evaluate Regularly
Use for Any Sport
❓ Frequently Asked Questions
What is the Kelly Criterion?
The Kelly Criterion is a formula that calculates the optimal fraction of your bankroll to wager on a bet to maximize long‑term growth, given your estimated win probability and the odds offered.
How do I use the Kelly Criterion calculator?
Enter your total bankroll, your estimated win probability (%), the American odds, and optionally a Kelly fraction (1 for full Kelly, 0.5 for half-Kelly). The calculator will show the optimal bet amount and fraction of bankroll.
What is a Kelly fraction?
Many bettors use a fraction of the full Kelly (e.g., 0.5 for half-Kelly) to reduce volatility. Full Kelly can be aggressive; half-Kelly is often recommended for beginners.
What does the formula calculate?
Kelly fraction f* = (p * b - q) / b, where p = win probability, q = 1-p, b = decimal odds minus 1 (net profit per unit stake). The result is the percentage of bankroll to bet.
Is the Kelly Criterion safe?
Full Kelly maximizes growth but can cause large swings. Using a fractional Kelly (e.g., half) reduces risk. Always bet responsibly and never exceed your comfort level.
Is this Kelly calculator free?
Yes, our Kelly Criterion calculator is completely free. No sign-up required. Use it to optimize your bet sizes.
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