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| Expected Value | -% |
| Fraction of Bankroll to Wager | -% |
What is Kelly Criterion Calculator?
The Kelly Criterion Calculator is a sophisticated tool designed to help you determine the optimal amount of your bankroll to wager on a bet. Rooted in probability theory, the Kelly Criterion aims to maximize your wealth in the long run by suggesting bet sizes that are proportional to both the odds and your perceived edge.
By inputting the decimal odds of your bet and your estimated probability of winning, this calculator provides the Kelly Criterion recommended percentage of your bankroll to wager. It's an essential tool for bettors looking to apply a mathematically sound approach to bankroll management and betting strategy.
How to Use the Kelly Criterion Calculator
1. Enter the decimal odds for your bet.
2. Input your estimated win probability as a percentage.
3. Optionally, adjust the Kelly Multiplier to apply a fraction of the full Kelly Criterion, useful for risk management.
4. If you wish to calculate the specific amount to wager, enable the "Bankroll" option and enter your total bankroll.
5. Click the "Calculate" button to determine the Kelly Criterion recommended bet size and the expected value of your bet.
Example
Suppose you've identified a betting opportunity with decimal odds of 3.0, and you estimate your probability of winning to be 40%. Using the Kelly Criterion Calculator:
- Enter 3.0 for the decimal odds.
- Enter 40% as your win probability.
- With a Kelly Multiplier of 1 (full Kelly), the calculator will recommend wagering approximately 8% of your bankroll.
This recommendation is based on maximizing long-term growth while managing the risk associated with the bet.
Frequently asked questions
What does the Kelly Criterion actually optimize?
Kelly sizes each bet to maximize the long-run growth rate of your bankroll — expected logarithmic wealth — rather than the profit on any single bet. Betting more than Kelly grows your bankroll slower and busts more often, even with the same edge.
Why do most bettors use half or quarter Kelly?
Full Kelly assumes your win probability is exactly right. In practice your estimate carries error, and overestimating your edge means systematically overbetting. Fractional Kelly gives up a little growth for a large cut in variance and drawdowns.
What does a negative Kelly stake mean?
It means the price offers you no edge — the implied probability of the odds is higher than your estimated win probability. The correct stake is zero; a negative number is the formula telling you to pass.
Should I use Kelly on parlays and props?
You can, but the estimate quality matters more than the formula. High-variance markets with wide margins (parlays, long-shot props) magnify estimation error, so most disciplined bettors use a smaller Kelly fraction there than on main lines.