How to use it
- Enter your bankrollThe money you keep for betting only, in naira.
- Enter the odds and your chanceThe decimal odds on offer and your own estimate that the bet wins.
- Choose the fractionFull Kelly is aggressive. Half or quarter Kelly is what most careful punters use.
The formula
Kelly share = (chance × odds minus 1) ÷ (odds minus 1). Suggested stake = bankroll × Kelly share × fraction. If the share is zero or below, there is no edge and no bet.
Worked example
Bankroll ₦50,000, odds 2.20, your chance 50%. Edge = 0.50 × 2.20 minus 1 = 10%. Kelly share = 0.10 ÷ 1.20 = 8.33%.
| Fraction | Share of bankroll | Stake |
|---|---|---|
| Full Kelly | 8.33% | ₦4,166.67 |
| Half Kelly | 4.17% | ₦2,083.33 |
| Quarter Kelly | 2.08% | ₦1,041.67 |
Kelly assumes your chance estimate is right. If it is too optimistic, full Kelly overbets fast. That is the main reason to use a fraction.
Kelly calculator FAQ
Why use half Kelly?
It gives up a little growth for much smaller swings, and it protects you when your estimates are a bit off.
Should I recalculate after every bet?
Kelly is designed around your current bankroll, so the stake grows after wins and shrinks after losses.
Can I use Kelly for accas?
Only with a sound chance estimate for the whole acca, which is hard. Most people use it for singles.
What if Kelly says no bet?
Then the odds do not pay enough for your estimate. Skip it. Our value betting guide explains why.