Expected Value (EV) is the cornerstone of profitable sports betting. A positive EV bet means the probability of winning — as you estimate it — exceeds the probability implied by the odds. Every professional bettor's primary goal is finding and betting +EV spots consistently.
To calculate EV: EV = (Win Probability × Net Profit) − (Loss Probability × Stake). If a book prices a line at -110 (implied probability 52.4%) but you believe the true win probability is 55%, that's a +EV bet worth taking.
The key challenge is estimating true probability better than the market. Models trained on game data, player performance, and situational factors can surface these edges. Even a 1-2% edge compounds over hundreds of bets.
EV explains why parlays are typically negative EV (vig stacks multiplicatively), why line shopping matters (better price = better EV), and why closing line value (CLV) is the best proxy for whether your process is sound. If you consistently beat the closing line, you're finding real edges before the market corrects.
Use the EV calculator on our Parlay EV guide to run scenarios.