How to use the Kelly calculator
- Odds — the price on offer, in any format.
- Bankroll — the money set aside for betting only.
- Your win chance — your estimate for this team.
- Pick full, half or quarter Kelly.
You'll see your edge, the full Kelly percentage, your fraction of the bankroll and the stake in dollars.
Example
Odds 2.30, your estimate 48%, bankroll $1,000:
| Value | |
|---|---|
| Edge | 0.48 × 2.30 − 1 = +10.4% |
| Full Kelly | (1.3 × 0.48 − 0.52) ÷ 1.3 = 8.0% → $80 |
| Half Kelly | 4.0% → $40 |
| Quarter Kelly | 2.0% → $20 |
Why small errors matter
Same odds of 2.30, $1,000 bankroll:
| Your win chance | Full Kelly | Quarter Kelly |
|---|---|---|
| 45% | 2.7% ($27) | 0.7% ($7) |
| 48% | 8.0% ($80) | 2.0% ($20) |
| 52% | 15.1% ($151) | 3.8% ($38) |
| 55% | 20.4% ($204) | 5.1% ($51) |
A ten-point change in your estimate (45% to 55%) makes the full Kelly stake more than seven times bigger. In esports, where a stand-in or a fresh patch can shift a match by that much, a fraction of Kelly is the sensible default.
Good habits with Kelly
- Recalculate as your bankroll changes: Kelly is a percentage, so stakes shrink after losses and grow after wins.
- Cap single bets: many bettors never go above 2–3% on one match, whatever the formula says.
- One bet at a time: Kelly assumes bets are independent. Several bets on the same match aren't.
Example: sizing a League of Legends bet
You find a League of Legends team at 2.10 and rate its chance at 52%, with a $1,000 bankroll.
| Value | |
|---|---|
| Edge | +9.2% |
| Full Kelly | 8.4% of bankroll ($84) |
| Half Kelly | 4.2% ($42) |
| Quarter Kelly | 2.1% ($21) |
Full Kelly asks for an 8.4% stake on one match, which is aggressive in a market where a stand-in or a patch can change a team overnight. Most bettors use a quarter or less in esports. That gives up some growth but keeps a bad run survivable, especially because esports estimates are noisier than in sports with decades of data.
If your estimate drops by only 2 points, to 50%, the edge falls to +5% and Kelly drops to about 4.5%. Small errors in the win chance move the stake a lot, which is why a fraction is safer.
Find your edge first with the expected value calculator. And keep it fun: set a budget and stick to it — read our responsible gambling page.
