Kelly Calculator

How this Kelly calculator works

The Kelly Criterion estimates how much of your bankroll to risk when you believe your edge is positive. It uses your estimated win probability and the payout implied by the odds.

• Full Kelly is the most aggressive mathematically optimal stake
• Half Kelly is a more conservative version many bettors prefer
• Quarter Kelly is even more cautious for volatile markets

This tool is only as good as your projected win probability. If your estimate is off, the suggested stake can be too aggressive.

What is the Kelly Criterion?

The Kelly Criterion is a bankroll-management formula that helps bettors size wagers when they believe they have an edge over the market. A Kelly calculator estimates how much of your bankroll to risk based on three inputs: your bankroll, the betting odds, and your projected win probability.

In sports betting, the Kelly Criterion is useful because it scales stake size with confidence. Bigger edges produce bigger suggested bets, while thin edges produce smaller ones or no bet at all.

What is Quarter Kelly?

A quarter Kelly calculator applies only 25% of the full Kelly recommendation. Many bettors prefer quarter Kelly because it reduces volatility, limits drawdowns, and still keeps bet sizing tied to perceived edge.

If full Kelly feels too aggressive, quarter Kelly is often the more practical real-world staking plan for sports betting.

Quarter Kelly vs Half Kelly vs Full Kelly

• Full Kelly: highest growth rate on paper, but the most aggressive and volatile.
• Half Kelly: a common middle ground that cuts variance while keeping meaningful exposure.
• Quarter Kelly: the most conservative of the three and often the easiest to stick with over a long season.

If you are unsure about your edge estimate, quarter Kelly is usually safer than full Kelly.

How to use this Kelly Calculator

1. Enter your current bankroll.
2. Enter the American odds for the bet.
3. Enter your own projected win probability.
4. Compare the suggested full Kelly, half Kelly, and quarter Kelly stake sizes.

If the calculator shows a negative or zero edge, that usually means there is no Kelly bet to make.

Kelly Calculator example

If your bankroll is $1,000, the line is -110, and you believe the bet wins 55% of the time, the Kelly Criterion will return a positive edge and suggest different stake sizes for full, half, and quarter Kelly. That gives you a quick way to choose between aggressive and conservative bankroll management.

FAQ

What is a Kelly calculator?
A Kelly calculator estimates optimal bet size using bankroll, odds, and projected win probability.

What is a quarter Kelly calculator?
A quarter Kelly calculator gives you 25% of the full Kelly stake, which many bettors use to reduce volatility.

Is quarter Kelly better than full Kelly?
Quarter Kelly is usually safer and easier to manage, while full Kelly is more aggressive and more volatile.

What win probability should I use?
You should use your own honest estimate of the bet’s chance to win. If that estimate is weak, Kelly outputs can become misleading.

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