Kelly Criterion Calculator
The Kelly Criterion gives the bet size that maximises long-run bankroll growth. Most pros use a fraction of full Kelly (½ or ¼) for lower variance.
Enter values and press Calculate.
Formula
f* = (bp − q) / b, where b = odds − 1, p = your win probability, q = 1 − p. A negative result means no edge — don't bet.
Important: Kelly is only optimal if your probability estimate is accurate. Most bettors overestimate their edge, so fractional Kelly (½ or ¼) is the practical safe choice.