Kelly stake calculator
A hypothetical fractional Kelly figure from your own win probability estimate and a price, never a recommended stake.
Your own estimate. The formula is only as good as this number.
Between 0 and 1. A quarter, 0.25, is a common conservative choice.
Hypothetical fractional Kelly
This is a hypothetical calculation conditional on your own win estimate, not a recommended stake. An estimate a few points too high turns a growth maximising fraction into a destructive one, which is why fractional Kelly exists at all. Slateline does not tell anyone what to risk.
How it is calculatedOpenClose
Full Kelly is the edge divided by the profit per unit, where the edge is the win probability times the profit per unit minus the loss probability. A fractional Kelly multiplies that by your chosen fraction. With no positive edge at the price, the formula returns zero.
- Full Kelly is the edge divided by the profit per unit. It maximises long run growth only if your probability estimate is correct.
- A fraction below 1 reduces both the growth rate and the size of the drawdowns. A quarter is a common conservative choice.
- With no positive edge at the price, the formula returns zero rather than a negative stake.
- This is a hypothetical calculation on your own estimate, never a recommended stake.
Worked example, illustrative
A 55% estimate at -110
- 1Profit per unit is 0.9091 and the break-even is 52.38%, so the edge is 2.62 points.
- 2Full Kelly is 5.50% of the bankroll.
- 3A quarter Kelly stake is 1.38% of the bankroll, which on 1,000 is 13.75.
These figures are an illustration of the formula, not a claim about any real market.
Related guidance
Research only. This tool does arithmetic on numbers you type. It does not place bets, submit entries, estimate a probability for you, or tell you what to risk. If gambling stops being fun, call 1-800-GAMBLER.