Expected Value (EV)

Expected value (EV) measures whether a wager is mathematically profitable over the long run. A positive-EV (+EV) bet wins more than it loses on average; a negative-EV bet loses money over time even if it occasionally hits. EV is the central metric for disciplined bettors because it separates good process from short-term luck — you can lose a +EV bet and still have made the correct decision.

The formula is EV = (P_win × profit_if_win) − (P_lose × stake), where P_win is your estimated true probability of winning and P_lose = 1 − P_win. For a $100 bet at +150 (decimal 2.50) with a true win probability of 45%: EV = (0.45 × $150) − (0.55 × $100) = $67.50 − $55.00 = +$12.50, or +12.5% of stake. Because the book pays out as if the chance were only 40%, the 5% edge in your favor produces positive EV.

The hard part is estimating the true win probability accurately. Most analytical workflows derive it from no-vig consensus odds at sharp books, then compare that fair probability against the price available at a softer book. When the available price implies a lower probability than the fair estimate, the bet carries positive EV. Garbage-in, garbage-out applies: a flawed probability estimate produces a meaningless EV number.