Kelly calculator
Optimal bet sizing given your edge. Enter your model probability, the offered odds, and your bankroll. We return full, half, and quarter Kelly stake recommendations plus your edge. Our default recommendation is quarter Kelly.
Decimal: 1.909
Edge
5.00%
Strong edge
Full Kelly is aggressive. At this level consider half Kelly. Double-check your probability estimate; strong edges are rare and often mean you have the wrong model.
Full Kelly
$55.00
Mathematical optimum. Aggressive.
Half Kelly
$27.50
Recommended for strong edges.
Quarter Kelly
$13.75
Our default. Buffers estimation error.
Why quarter Kelly by default
Full Kelly assumes you know your true probability. You do not. Your model estimate is itself noisy; so is the price. If you overestimate your edge by 20 percent at full Kelly, you can lose 40+ percent of your bankroll in a normal losing stretch that would look recoverable at quarter Kelly.
Quarter Kelly gives up about 25 percent of the theoretical growth rate in exchange for dramatically lower variance and much better behavior when your probability estimate is wrong. Most professional bankroll managers run between quarter Kelly and half Kelly in practice. Full Kelly is a textbook optimum, not a field-tested recommendation.
CLV essay · CLV calculator · No-vig calculator
Full Kelly assumes you know your true probability. You do not. Your model estimate is itself noisy; so is the price. If you overestimate your edge by 20 percent at full Kelly, you can lose 40+ percent of your bankroll in a normal losing stretch that would look recoverable at quarter Kelly.
Quarter Kelly gives up about 25 percent of the theoretical growth rate in exchange for dramatically lower variance and much better behavior when your probability estimate is wrong. Most professional bankroll managers run between quarter Kelly and half Kelly in practice. Full Kelly is a textbook optimum, not a field-tested recommendation.
CLV essay · CLV calculator · No-vig calculator