EV Calculator (Expected Value for Sports Betting)

What is expected value (EV) in betting?

Expected value is the average amount a bet would win or lose if you could place it thousands of times. It's the single most important number in sports betting, because it separates bets that are profitable in the long run (+EV, positive expected value) from bets that only look good (−EV). Sharp bettors don't chase wins — they place +EV bets over and over and let the math play out.

A bet is +EV whenever the odds you're offered pay more than the true probability of the outcome deserves. The catch is knowing that true probability. Sportsbook prices don't tell you directly, because every price has vig (margin) baked in. That's where devigging comes in.

The expected value formula

For a single bet: EV = (fair win probability × profit if you win) − (probability you lose × amount staked). Divide the result by your stake to express it as a percentage. A +2% EV means that for every $100 you stake on bets like this, you expect to net $2 in profit over the long run — small per bet, but decisive across hundreds of bets.

A worked example

Say a book offers you +120 (decimal 2.20) on a team you believe has a true 50% chance to win, and you stake $100. If it wins, you profit $120; if it loses, you're out $100. EV = (0.50 × $120) − (0.50 × $100) = $60 − $50 = +$10, or +10% EV. The fair (break-even) price for a 50% shot is +100, so being offered +120 is a clear edge. The calculator above runs this math instantly and flags whether the bet clears the fair line.

Where the "fair" probability comes from — devigging

You rarely know a bet's true probability outright. The standard method is to take a sharp book (Pinnacle, Circa) — books so efficient their prices closely track real probabilities — and remove the vig from their line to estimate the fair probability. That's exactly what the "Devig a sharp line" mode does: paste both sides of the sharp market, and the calculator devigs it (using the most-conservative method) to produce the fair win probability, then measures your book's price against it. This is the foundation of value betting — and it's precisely how the DawBets +EV feed works under the hood, across 25+ books in real time.

When to use this calculator

Use the EV calculator any time you're about to place a bet and want to know if it's actually worth it. The fastest workflow: open a sharp book like Pinnacle, copy both sides of the market into the "Devig a sharp line" mode to get the fair probability, then enter the price your book is offering. If the EV comes back positive, the bet has a long-run edge; if it's negative, you're paying too much vig to make it worthwhile.

Already know your true probability (from a model or your own read)? Use "Fair win %" mode instead. Want to size the bet once you've confirmed it's +EV? The Kelly calculator turns your edge into an optimal wager. Just want the no-vig fair odds? Use the devig calculator. To skip the manual work entirely and get live +EV bets across every book, the DawBets feed does the devigging and line shopping for you.

Frequently asked questions