Free Kelly criterion calculator. Enter win probability, odds, and bankroll to get the optimal stake — plus safer half and quarter Kelly sizing.
The Kelly criterion sizes each bet to maximize long-run bankroll growth — more when your edge is large and odds are long, less when the edge is thin. Full Kelly is optimal but volatile; most bettors use half or quarter Kelly to cut variance.
Kelly assumes your probability estimate is accurate. Over-estimate your edge and full Kelly will over-bet. When in doubt, size down.
Most bettors use half or quarter Kelly — a little less growth for far lower volatility.
A 0% or negative result means no positive expected value at that price — pass on the bet.