EV Betting Calculator
Enter the odds you're being offered and the fair (no-vig) odds for the same outcome. This expected value calculator instantly tells you the EV, your edge in percent, and whether the bet is genuinely +EV — plus the Kelly-optimal stake.
How the math works
Expected value is the average profit you'd make on a bet if you could place it an infinite number of times. It hinges on one thing: the true probability of the outcome versus the probability the book's price implies.
If your book is paying +150 (decimal 2.50) on something whose fair price is +130 (an implied 43.5% chance), you're getting paid more than the risk deserves. That gap is your edge — and over hundreds of bets, edge is the only thing that matters. The formula runs on decimal odds, so if you're working from a US price, the American odds converter will flip it (and show the implied probability) in one step.
Where do the "fair odds" come from?
The calculator is only as good as the fair number you feed it. Sharp bettors get it by removing the vig from a sharp book like Pinnacle, whose lines are the closest thing the market has to true probability. Do that, compare it to what softer US books are posting, and the mispriced bets fall out. See the full method in What Is +EV Betting?
Frequently asked questions
How do you calculate expected value on a bet?
Expected value equals the probability of winning times the profit if you win, minus the probability of losing times the amount you stake. Using fair (no-vig) win probability p, a stake S, and decimal odds d: EV = p × (d − 1) × S − (1 − p) × S. A positive result is a +EV bet.
What is a good EV percentage in sports betting?
EV% is the expected profit as a percentage of your stake. Any positive number is theoretically profitable long term. Sharp bettors typically act on edges of roughly 1–5%; anything much higher usually signals a stale line or an input error worth double-checking.
Where do I get the fair odds to compare against?
The fair odds are the true, no-vig probability of the outcome. Most +EV bettors derive them by removing the vig from a sharp book like Pinnacle. Iron Marker does this automatically across every major US sportsbook in real time.
Stop pricing bets one at a time.
Iron Marker removes the vig from the sharp line and scans every major US sportsbook in real time, surfacing only the bets that are genuinely +EV — with the Kelly stake already calculated. $39/mo, 7-day free trial.
Start free trialIron Marker is an analytics tool, not a sportsbook, and this calculator is educational — not betting or financial advice. Must be 21+. Problem gambling? Call 1-800-GAMBLER.