Calculate EV and ROI to find profitable betting opportunities
Expected Value (EV) is the single most important concept in professional sports betting mathematics. It represents the average amount you can expect to win or lose per bet over the long run, calculated by multiplying your win probability by potential profit and subtracting your loss probability multiplied by stake amount. Positive EV (+EV) bets are the holy grail of sports betting—these are wagers where the odds offered by the bookmaker are better than the true probability of the outcome, creating a mathematical edge for the bettor across NFL, NBA, NHL, MLB, NCAAF, and soccer markets.
Our EV calculator instantly determines whether a bet has positive or negative expected value by comparing bookmaker odds against your assessed true probability. For example, if you believe an NBA team has a 55% chance to cover the spread, but the odds imply only 50% probability (even money), you've found a +EV opportunity worth 5% edge. Over hundreds of bets, this edge compounds into significant profits. The calculator also computes ROI (Return on Investment) percentage, showing exactly how much profit you can expect per dollar wagered when repeating similar edges repeatedly.
Professional bettors never place wagers without first calculating EV. This discipline separates gamblers from investors—winning bettors understand that short-term variance is irrelevant if the underlying mathematics are sound. By consistently identifying and betting only +EV opportunities, you guarantee long-term profitability regardless of individual game outcomes. Use this tool to validate every bet against your probability models, historical data, and expert analysis from BetLegend to ensure every dollar wagered carries a positive mathematical expectation for sustained bankroll growth.
Your wager amount in dollars
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Your estimated chance of winning
Fill in all fields to see if this bet has positive expected value
The Ravens are 3-point favorites (-110) against the Steelers in a divisional matchup. Your statistical model accounts for Baltimore's elite defense, Pittsburgh's offensive line injuries, and the historical tendency for divisional games to be closer than the spread suggests. Your model gives Baltimore a 58% chance to cover the 3-point spread. Let's calculate the EV: With -110 odds, you risk $110 to win $100 on a $110 bet. EV = (0.58 Ă— $100) - (0.42 Ă— $110) = $58 - $46.20 = +$11.80. That's a ROI of 10.7%, making this a strong +EV play worth betting.
LeBron James is listed at over 25.5 points (-115) against a defense ranked 28th in defensive efficiency. The Lakers' two other primary scorers are injured, meaning LeBron will have an elevated usage rate. Your analysis of similar game scripts over the past three seasons shows LeBron hitting this number 68% of the time under these conditions, but the bookmaker's -115 odds imply only a 53.5% probability. This 14.5 percentage point edge represents significant +EV. On a $100 bet: EV = (0.68 Ă— $87) - (0.32 Ă— $100) = $59.16 - $32 = +$27.16, a massive 27% ROI that professional bettors would hammer.
The Avalanche and Oilers total is set at 6.5 goals with the Over at -105. Both teams rank top-5 in goals per game, and your analysis incorporates rink temperature data (warmer ice leads to faster gameplay and more goals), recent goalie performance, and special teams efficiency. You estimate a 57% chance the game goes over 6.5 goals, while -105 odds imply a 51.2% probability. EV = (0.57 Ă— $95.24) - (0.43 Ă— $100) = $54.29 - $43 = +$11.29 on a $100 bet, offering 11.3% ROI. This edge exists because the betting public undervalues temperature data that sharp bettors have quantified.
It's the 7th inning and the Yankees lead the Red Sox 3-2. The live moneyline shows Yankees -180 to win. However, Boston's bullpen has a 2.87 ERA over the last 15 games while New York's closer is dealing with a minor injury and their setup man was used heavily yesterday. Your model gives the Yankees only a 62% chance to hold this lead, but -180 odds imply a 64.3% probability. This is actually a -EV situation despite the Yankees leading. EV = (0.62 × $55.56) - (0.38 × $100) = $34.45 - $38 = -$3.55, representing -3.6% ROI. This demonstrates why not every bet on a team leading is +EV—the price matters more than the situation. Pass on this bet.