Kelly Criterion Calculator — optimal sports betting stake size
The Kelly criterion turns your edge into a stake size. Enter the price, your true win probability and your bankroll to see full, half and quarter Kelly recommendations.
Implied probability
45.45%
Edge (EV per $1)
10.00%
Kelly fraction
8.33%
Full Kelly stake
$83.33
Half Kelly stake
$41.67
Most common in practice
Quarter Kelly stake
$20.83
The Kelly formula
Kelly fraction = (b × p − q) ÷ b, where b is decimal odds minus 1, p is your true win probability and q is 1 − p. A negative result means the bet has no edge at that price.
Why most bettors use half or quarter Kelly
Full Kelly is only optimal if your probability estimate is exactly right. Because prop models carry estimation error, fractional Kelly (half or quarter) keeps most of the long-run growth while cutting drawdowns and variance sharply.
Get an accurate win probability first
Kelly is only as good as its input. Strip the sportsbook margin out of a market with the devig calculator or convert a price with the odds converter before sizing a bet.