Kelly Criterion Calculator
Find the mathematically optimal bet size based on your edge and bankroll using the Kelly Criterion formula.
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What Is the Kelly Criterion?
The Kelly Criterion is a formula that determines the optimal bet size to maximize long-term bankroll growth. It balances risk and reward by betting more when you have a larger edge and less when the edge is slim.
The Formula
f* = (bp - q) / b
- b = decimal odds - 1 (the profit per dollar wagered)
- p = probability of winning
- q = probability of losing (1 - p)
Why Use Half Kelly?
Full Kelly can be aggressive with large swings. Most professional bettors use half Kelly or quarter Kelly to reduce variance while still capturing most of the long-term growth advantage.
Frequently Asked Questions
What is the Kelly Criterion in sports betting?
The Kelly Criterion is a mathematical formula that calculates the optimal percentage of your bankroll to wager on a bet based on your edge and the odds offered. It maximizes long-term bankroll growth by betting more when your edge is large and less when your edge is small.
Should you use full Kelly or fractional Kelly?
Most professional bettors use fractional Kelly, typically half Kelly or quarter Kelly. Full Kelly is mathematically optimal for growth but produces large swings that are uncomfortable for most people. Half Kelly captures about 75% of the growth rate of full Kelly while cutting the variance roughly in half.
What is fractional Kelly betting?
Fractional Kelly means betting a fraction of the full Kelly recommendation. For example, if full Kelly says to bet 10% of your bankroll, half Kelly would bet 5% and quarter Kelly would bet 2.5%. This approach reduces volatility and protects against errors in your probability estimates while still growing your bankroll over time.
What happens if the Kelly Criterion gives a negative number?
A negative Kelly result means the bet has negative expected value and you should not place it. The formula only recommends a bet size when you have a genuine edge. If the result is zero or negative, the odds do not offer enough value relative to your estimated win probability.
Get the Edge with Optimal Bet
Our app scans sportsbook pricing across the market to expose inefficiencies and uncover +EV edges. We compare odds, surface high-value opportunities, and deliver precision alerts so you can move with conviction.
