Kelly bet sizing calculator
Turn bankroll, price, and conviction into a disciplined fractional-Kelly stake.
▲$104.17
Quarter Kelly is 2.1% of $5,000: $104.17. Full is $416.67.
- Bankroll fraction
- 2.08%
- Full Kelly
- 8.33%
- Expected ROI
- 12.50%
Full Kelly grows a bankroll fastest but swings hard, so most bettors stake a half or a quarter.
How to use the Kelly bet sizing calculator
The Kelly criterion connects your estimated edge with bankroll size. Fractional Kelly reduces volatility by staking only part of the full recommendation.
- 1Enter your bankroll, offered odds, and projected win probability.
- 2Choose full, half, quarter, or another Kelly fraction.
- 3Use the suggested stake as a sizing reference, not a requirement.
Formula and assumptions
Kelly fraction = (decimal profit multiple × win probability - loss probability) / decimal profit multiple.
Kelly sizing assumes your probability estimate is accurate and your bankroll is dedicated to this strategy. Overconfidence can lead to oversized bets.
The math in full, with worked examples: The Kelly criterion for sports betting
Questions
Answers about this free Kelly bet sizing calculator, sports betting odds, payouts, and the math behind each result.
- Fractional Kelly lowers stake size and bankroll volatility while preserving some of the method's growth-based logic.
- The Kelly recommendation is zero or negative, which indicates that the entered price does not justify a bet under your probability estimate.