Calculators / Kelly criterion
Kelly criterion calculator
Having an edge is only half the job — sizing the stake correctly is the other half. Kelly gives the bankroll fraction that maximizes long-run growth.
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Edge:
Full Kelly (% of bankroll)
Full Kelly stake
Half Kelly stake
Quarter Kelly stake
How it works
Full Kelly is (bp − q) / b, where b is the net decimal odds (price minus one), p is your probability of winning and q is one minus p. It is the fraction of bankroll that maximizes long-run geometric growth.
Full Kelly is volatile. A single bad run can be brutal even when the edge is real. Most bettors who use it at all stake a fraction of the fraction: half or quarter Kelly trades some growth for a much smoother ride.
Worked example
| Odds | 2.50 (+150) |
| Your probability | 45.0% |
| Edge | +5.0% |
| Full Kelly | 8.3% of bankroll |
| Half Kelly, $1,000 bankroll | $41.67 |