Expected Value (EV)

Expected value, or EV, is a statistical measure of a bet’s average outcome if you repeated it many times under the same conditions. Calculate it by multiplying each possible outcome by its probability, then summing the products. Positive expected value (+EV) means a bet profits over the long run; negative expected value (-EV) means you lose money over time. For professional and serious recreational bettors, EV is the single most important metric for deciding whether a wager is worth placing.

Using EV means separating the result of one bet from the math behind it. A +EV bet can still lose on any given night, and a -EV bet can still win. What counts is the pattern across hundreds or thousands of wagers. Bettors who consistently find and place +EV bets generate profit over a large enough sample. Those who consistently take -EV bets watch their bankroll erode, regardless of short-term winning streaks.

Example

Say you estimate a team has a 55% chance to win, and the book offers +110 (decimal 2.10) on that team. The EV calculation for a $100 bet: (0.55 x $110) - (0.45 x $100) = $60.50 - $45.00 = +$15.50. So on average you’d expect $15.50 profit for every $100 wagered on this type of bet over the long run. You lose 45% of the time, but the payout when you win more than covers those losses.

Key Points

• Basis of profit: Every winning long-term strategy is built on finding and exploiting positive expected value.
• Needs accurate probabilities: An EV calculation is only as good as your estimate of each outcome’s true probability.
• Short-term results vary: A single bet or a run of bets can diverge sharply from the expected value due to variance.
• The book’s edge is built in: Most bets a sportsbook offers carry negative expected value for you, because the odds include a margin (vig) favoring the house.
• Comparison tool: EV lets you rank different wagers on one scale, regardless of sport, bet type, or odds format.