Kelly Criterion Calculator
Find the mathematically optimal stake based on your bankroll and your edge.
Bankroll & Bet
+150 · 2.50 · 3/2 · 40.0%
Most professionals use a fraction of Kelly to reduce variance.
Recommendation
You have a mathematical edge.
Recommended wager:
$41.67
Bankroll %4.17%
Full Kelly8.33%
How to use this tool
- Enter your total bankroll.
- Enter the price (any format) and your honest true win probability.
- Pick a Kelly fraction — most bettors use Half or Quarter — and stake the recommended amount.
The formula
f = (b·p − q) / b- f = fraction of bankroll to stake
- b = decimal odds − 1 (net odds)
- p = true win probability, q = 1 − p
Worked example
+150 (b = 1.5) with a true probability of 45%: f = (1.5 × 0.45 − 0.55) / 1.5 ≈ 8.33%full Kelly. Half Kelly on a $1,000 bankroll ⇒ a $41.67 bet.
Prediction markets: price a contract as odds (40¢ that settles at $1 ≈ +150) and use the market or a model for the probability — Kelly sizes the position the same way.