Kelly Criterion Calculator
Advertising
How to use the Kelly Criterion calculator
Pick your odds format and enter the odds, then type your own estimate of the win chance as a percentage and your total bankroll. Choose a Kelly fraction: Full uses the raw formula, while Half and Quarter scale it down for safety. The calculator shows the stake to place, that stake as a share of your bankroll, and your edge as expected value per unit. If your win chance is no better than the odds imply, it tells you there is no positive edge and that the model says not to bet. Decimal is the format Canadian sportsbooks show by default.
The terms in short
- Kelly Criterion: a formula for the stake size that maximises long-term bankroll growth when you have an edge.
- Win chance: your own estimate of how often the bet wins, not the odds.
- Edge (EV per unit): the average profit per unit staked if your estimate is right. No edge means no Kelly stake.
- Full / Half / Quarter Kelly: the full stake or a scaled-down version that trades a little growth for much lower swings.
How the stake is calculated
With b as the net decimal odds, p your win chance and q the chance of losing:
- Net odds
b = decimal − 1 - Kelly fraction
f = (b × p − q) ÷ b - Stake
bankroll × f × Kelly fraction - Edge (EV / unit)
(p × decimal) − 1 - Fractional → Decimal
(top ÷ bottom) + 1 - American → Decimal
+: odds ÷ 100 + 1 · −: 100 ÷ |odds| + 1
Why most people use a fraction of Kelly
Full Kelly assumes you know the true win chance, and in real betting that estimate is almost always a bit off. When it is too high, full Kelly overbets badly and the swings can wipe out a bankroll even with a real edge. That is why half or quarter Kelly is the common choice: it keeps most of the growth with far smaller drops. Treat any Kelly stake as an upper limit, never bet money you cannot afford to lose, and remember the formula only helps when your edge is genuinely positive.
For information only. 19+ (18+ in AB, MB and QC). Please play responsibly.