Kelly Criterion Calculator
Select Odds Type:
%
| Expected Value | -% |
| Fraction of Bankroll to Wager | -% |
What it does
The Kelly criterion sizes a bet to grow your bankroll fastest over time, based on the odds and your edge. This Kelly criterion calculator gives the full stake and any fraction of it. Many bettors stake a fraction of it (half or quarter Kelly) to cut the swings. Related: how many bets it takes to prove an edge.
How to use
Pick the odds type and enter the odds.
Enter your win percentage.
Set the Kelly multiplier (1 = full Kelly, 0.5 = half). Tick Enable Bankroll for a dollar amount.
Click Calculate.
Worked example
Decimal 3.0 with a 40% win chance
- Profit per $1
- 2.0
- Kelly fraction
- 0.40 - 0.60 ÷ 2 = 0.10
- EV
- +20% per dollar
- Half Kelly
- 5% of bankroll
- Full Kelly
- 10% of bankroll
FAQ
What is the Kelly criterion formula?
Kelly stake = (b × p - q) / b, where b is the decimal odds minus 1, p is your win chance and q is 1 - p. At +100 with a 55% win chance: (1 × 0.55 - 0.45) / 1 = 10% of your bankroll.
What does the Kelly Criterion actually optimize?
The long-run growth rate of your bankroll, not the profit on any one bet. Betting more than Kelly grows your bankroll slower and busts it more often.
Why do most bettors use half or quarter Kelly?
Full Kelly assumes your win probability is exact. Your estimate has error, so a fraction of Kelly gives up a little growth for much smaller swings.
What does a negative Kelly stake mean?
The odds' implied probability is higher than your win probability, so you have no edge. The right stake is zero.
Should I use Kelly on parlays and props?
You can, but wide-margin, high-variance bets magnify errors in your estimate, so use a smaller fraction there.