Kelly Criterion
Enter the target odds and the fair odds (from the Fair Odds calculator) to get the optimal stake for your bankroll.
The odds offered by your bookmaker
From your Fair Odds calculator
Your total capital dedicated to betting
Full Kelly
Maximum growth — high risk
Half Kelly
Recommended for value betting
Quarter Kelly
Conservative — low variance
Calculation details
Understanding the Kelly criterion
The problem Kelly solves
You have identified a +EV bet. But how much should you stake? Too little and you underexploit your edge. Too much and a bad run can wipe you out before the law of large numbers works in your favor. Kelly answers exactly that question.
The formula
Kelly computes the optimal fraction of your bankroll to stake in order to maximize the geometric growth of your capital over the long run. It depends on two parameters: your mathematical edge (EV) and the net profit if you win.
Why half Kelly is recommended
Full Kelly is mathematically optimal but assumes your estimate of the fair odds is perfect, which is never the case. In practice, value bettors use half Kelly: it keeps 75% of full Kelly's theoretical growth while cutting variance in half and drastically reducing the risk of ruin.
Quarter Kelly to start out right
If you are just starting out or have a low tolerance for variance, quarter Kelly is advised. You stake 25% of the optimal amount, growth is slower, but losing streaks remain psychologically manageable and let you stay in the game over time.
Strategy comparison
| Strategy | Stake | Growth | Variance | Who is it for? |
|---|---|---|---|---|
| Full Kelly | f* | 100% | Very high | Experienced trader |
| Half Kelly | f*/2 | ~75% | Moderate | Active value bettor |
| Quarter Kelly | f*/4 | ~50% | Low | Beginner |