Calculators / Kelly Criterion

Kelly Criterion Stake Calculator

Kelly sizes a bet from your estimated edge. Overestimating probability blows up bankrolls. Use fractional Kelly and never bet money you cannot afford to lose.

Formula

f* = (b p − q) / b where b = decimal−1, p = win probability, q = 1−p.

Worked examples

Even money, 55% estimated. Full Kelly = 10% of bankroll. Half Kelly = 5%.

FAQ

Why half Kelly?

Estimation error is common. Half or quarter Kelly cuts volatility.

Related: bet-payout no-vig

Research tool only. Never risk money you cannot afford to lose. Help: ncpgambling.org.