Bankroll in dollars, American odds, your win percent, and full, half, or quarter Kelly.

Why is the implied percent not the win percent?

The price implies a break-even percent, hold included. Kelly uses your own win percent, the one you type in.

What if the edge is negative?

The page shows no stake. Kelly says sit this one out.

Does half Kelly change the formula?

No. It multiplies the full fraction by 0.5, then by the bankroll. Quarter Kelly uses 0.25.

Does this use my bet tracker?

No. It only uses the numbers in the form. No account needed.

Kelly Criterion Calculator

Kelly turns your bankroll, an American price, and your win percent into a stake, sized as a percent of bankroll. Half and quarter Kelly are the same math with a smaller fraction.

The form takes American odds only, like +150 or -110. It uses the win percent you type, not the one implied by the price.

The formula

b is the net profit on 1 unit. At +150, b is 1.50. At -110, b is 100/110, about 0.909.

Full Kelly is (b times p, minus q) / b. p is your win percent as a decimal. q is 1 - p.

The page multiplies full Kelly by your fraction, then by your bankroll. If full Kelly is zero or below, you get no stake.

Example 1

Bankroll $1,000, odds +150, win percent 45, half Kelly.

The price implies 40.0%. Full Kelly is 8.33%. Fraction used is 50%. Bankroll percent is 4.17%. Stake is $41.67.

Example 2

Bankroll $5,000, odds -110, win percent 55, quarter Kelly.

The price implies 52.4%. Full Kelly is 5.50%. Fraction used is 25%. Bankroll percent is 1.38%. Stake is $68.75.

No bet

-110 at a 30% win chance, any fraction. Full Kelly is negative. The stake rows stay hidden. The line is: "No edge at that win percent. Kelly says sit this one out."

Limits

Full Kelly can be a large share of the bankroll. Half and quarter Kelly bet less of it. This page doesn't place the bet or know your real bankroll.

Runs in your browser. Nothing is sent to EdgeTilt. For your own math, not betting advice.

Kelly criterion