Expected Value Calculator
A bet is worth making when the price pays more than the true odds — that gap is your edge. This expected value calculator de-vigs the sharp line to find the fair probability, then compares it to the price at your book. Enter the numbers below; the +EV math is computed live, every step shown.
Want the full animated derivation and a live +EV feed across books? Open the tool in the app →
How the expected value calculation works
Expected value is the average result of a bet if you could place it over and over. For a bet that wins with probability p and pays net decimal odds b per unit staked, the +EV calculator uses:
The first term is what you win when you’re right, weighted by how often that happens; the second is the stake you lose the rest of the time. When EV is positive the bet has positive expected value — the price pays more than the risk is worth.
The whole game is getting p right. A book’s own price can’t tell you: it has vig baked in, so its implied probability is inflated. So this ev betting calculator takes a sharp or fair line, de-vigs it to a true probability, and compares that to what your price implies:
If the de-vigged fair probability p beats the probability your price implies, the edge is positive and so is the EV. The proportional, power, and Shin methods de-vig the sharp line differently — the calculator above lets you switch between all three.
Does your edge survive the method choice?
Here’s the trap no other +EV calculator shows you: a thin edge can be an artifact of the de-vig method. Proportional, power, and Shin split the vig between favorite and longshot differently, so on a small edge they can disagree about whether a bet is even +EV. The result panel above computes your EV under all three at once and tells you whether the edge holds up: an edge that’s positive under proportional, power, and Shin is real; one that’s +EV under a single method and negative under another is fragile — worth a much smaller stake, or none. Showing the worst case, not just the flattering one, is the honest version of this math.
Worked example
The sharp line is −140 / +120. De-vig it proportionally to find side B’s fair probability:
Your book offers +130 on side B, a net payout of b = 1.30. Its implied probability is lower than fair, so the edge is positive:
De-vigging is the engine underneath all of this — see the no-vig calculator for the fair-line step on its own, and Expected Value (+EV) Betting for the full method with the animated derivation. Once you have a +EV bet, the Kelly calculator sizes it, and closing line value tells you whether the edge was real.
Frequently asked questions
What is an expected value calculator?
An expected value calculator estimates the long-run average return of a bet. It de-vigs the sharp or fair line to get a true probability, then compares that to the probability your book’s price implies. When the fair probability is higher than the price implies, the bet has positive expected value (+EV).
How do you calculate the expected value of a bet?
Use EV = p·b − (1−p), where p is the fair (de-vigged) win probability and b is the net decimal payout of your price. A positive result means the bet returns more than it risks on average; a negative result means the price is worse than fair. Multiply by your stake to get expected profit per bet.
What makes a bet +EV?
A bet is +EV (positive expected value) when the de-vigged fair probability beats the probability your price implies. In practice you find the fair probability from a sharp or consensus line, remove its vig, and check whether a softer book is offering a price generous enough that the math clears zero.