Expected Value Calculator: finding profitable bets
Expected value (EV) tells you how much a bet will earn or lose on average over a large number of repetitions. Positive EV means the bet is profitable for you in the long run. Negative EV means the sportsbook has the edge. This is the core idea behind value betting.
The formula is straightforward: EV = (win probability × profit) − (loss probability × stake). Let's walk through an example. A bookmaker offers 2.10 on an outcome, and you estimate the true probability at 50%. With a $100 stake: EV = 0.50 × $110 − 0.50 × $100 = $55 − $50 = +$5. On average, every bet like this earns you $5.
The big question: where do you get the "real" probability? The most reliable method is to take odds from the sharpest book on the market and strip the margin. Pinnacle is the go-to benchmark for most bettors. Run their odds through a margin calculator, get the fair probability, and plug it in here.
ROI expresses the same thing as a percentage of your stake. An EV of +$5 on a $100 bet equals +5% ROI. Professional bettors typically sustain ROI between 2% and 10% over the long haul. The one rule that matters: only bet when the expected value is positive.