EV Calculator
Work out the expected value (EV) of a bet before you place it. Enter your own estimate of a selection's chance of winning and the bookmaker's odds, and the calculator shows your edge, your EV per bet, and a fractional Kelly stake suggestion.
EV Calculator
Worked Example
You think a team has a 55% chance to win. The bookmaker offers 2.00 (which implies a 50% chance). On a 10.00 stake:
That +1.00 is not a guaranteed profit — it is the average result if that exact bet were repeated many times at those odds with your probability estimate being correct. Any single bet still wins or loses in full.
How This Calculator Works
Implied Probability
The bookmaker's odds imply a probability: 1 ÷ decimal odds. At odds of 2.00 that is 50%. If you think the true chance is higher than that, the bookmaker's price contains an edge for you.
Expected Value
EV per unit staked is (probability × decimal odds) − 1. This is not the same as the edge in percentage points — EV also scales with the size of the odds, so two bets with the same edge can have very different EV.
Quarter Kelly Stake
Full Kelly stake sizing is f = (bp − q) ÷ b, where b is the odds minus 1, p is your probability and q is 1 − p. This calculator shows a quarter of that figure — more conservative sizing, since full Kelly assumes your probability estimate is exactly right.
The Probability Estimate Is the Hard Part
The maths above is exact. What is not exact is your probability estimate. This calculator cannot verify whether your read on a match is right — it can only tell you what follows if it is.
Frequently Asked Questions
No. A positive EV bet can still lose more often than it wins if the odds are long — EV describes the average outcome across many repeats of the same bet at the same odds and probability, not the result of any single bet.
This calculator does not supply one. You need your own view — from form, statistics, or specialist knowledge — of how likely a selection is to win. The calculator only shows what that estimate implies once compared with the odds on offer.
Edge is the gap in probability points between your estimate and the bookmaker's implied probability. EV also multiplies that gap by the odds on offer, because a winning bet at long odds returns far more than a winning bet at short odds.
Full Kelly assumes your probability estimate is exactly correct, which is rarely true in sports betting. Quarter Kelly stakes a quarter of the full Kelly figure, reducing the impact of an overconfident estimate and smoothing out variance.
Bet Responsibly
This calculator is for informational purposes only and does not predict outcomes. Set a budget before you bet, never chase losses, and take breaks if gambling stops being fun. If you're concerned about your gambling, help is available.