Expected Value (EV)

Expected value, abbreviated EV, is a statistical measure of a bet’s average outcome were it repeated many times under identical conditions. It is computed by multiplying each possible outcome by its probability and summing the products. Positive expected value (+EV) marks a bet as profitable over the long run; negative expected value (-EV) means the bettor should expect to lose money over time. Professional and serious recreational bettors regard EV as the single most important gauge of whether a wager merits placing.

Grasping EV means decoupling the result of one bet from the mathematical edge underneath it. A +EV bet can still lose on any single occasion, and a -EV bet can still win. What counts is the pattern across hundreds or thousands of wagers. Bettors who reliably find and place +EV bets will, over a large enough sample, turn a profit. Those who reliably take -EV bets will watch their bankroll drain, whatever short-term streaks intervene.

Example

Suppose you estimate a team’s win chance at 55%, and the book offers +110 (decimal 2.10) on that team. The EV of a $100 bet is: (0.55 x $110) - (0.45 x $100) = $60.50 - $45.00 = +$15.50. On average, then, you would expect $15.50 profit per $100 wagered on this type of bet over the long run. Even though you lose 45% of the time, the winning payout more than offsets those losses.

Key Points

• Foundation of profitable betting: Every durable long-term strategy rests on finding and exploiting positive expected value.
• Requires accurate probability estimates: An EV calculation is only as useful as your estimate of each outcome’s true probability.
• Short-term results may differ: A single bet, or even a run of them, can stray far from expected value because of variance.
• The bookmaker’s edge is built-in: Most bets a book offers carry negative expected value for the bettor, since the price embeds a margin (vig) favoring the house.
• Comparison tool: EV places different wagers on a common scale, regardless of sport, bet type, or odds format.