How to Calculate Expected Value

Expected value measures the average outcome of a bet if it were placed thousands of times. A positive EV means you make money long-term; negative EV means you lose to the house. The formula:

EV = (Win Probability × Net Profit) − (Lose Probability × Stake) EV % = EV / Stake × 100 Where: Net Profit = Stake × (Decimal Odds − 1) Lose Probability = 1 − Win Probability

Example

You bet $100 on a team at +150 (decimal 2.50). Your model gives them a 45% win probability.
Net profit if win: $100 × (2.50 − 1) = $150
EV = (0.45 × $150) − (0.55 × $100) = $67.50 − $55.00 = +$12.50
EV% = $12.50 / $100 = +12.5% — a strong positive edge.

What Is +EV Betting?

Positive expected value (+EV) betting means finding wagers where your estimated probability of winning is higher than the sportsbook's implied probability. Over hundreds of bets, +EV betting produces profit even through losing streaks.

The key is having an accurate model for true win probability. Sportsbooks set their lines to be slightly worse than fair — the juice (vig) builds in their edge. Beat the vig with a superior probability estimate and you flip the advantage.

Book Implied Probability vs True Probability

If a sportsbook offers -110 on both sides, the implied probability of each is 52.4% (not 50%). That 2.4% excess is their vig. To profit long-term, your win estimate must consistently exceed the book's implied probability — not just equal it.

EV Is Long-Term — Sample Size Matters

A +10% EV bet still loses 40–60% of the time depending on the odds. Short-term results are noisy. Profitable bettors track EV across hundreds of picks to measure their true edge, not bet-by-bet results.

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