Expected Value (EV)

Expected value, commonly abbreviated as EV, is a statistical measure that represents the average outcome of a bet if it were repeated many times under the same conditions. It is calculated by multiplying each possible outcome by its probability and then summing those products. A positive expected value (+EV) indicates that a bet is profitable over the long run, while a negative expected value (-EV) means the bettor can expect to lose money over time. Professional and serious recreational bettors treat expected value as the single most important metric for evaluating whether a wager is worth placing.

Understanding EV requires separating the result of a single bet from the mathematical edge behind it. A +EV bet can still lose on any given occasion, and a -EV bet can still win. What matters is the pattern that emerges across hundreds or thousands of wagers. Bettors who consistently find and place +EV bets will, over a large enough sample, generate profit. Those who consistently take -EV bets will see their bankroll erode, regardless of any short-term winning streaks.

Example

Suppose you estimate that a team has a 55% chance of winning a game, and the bookmaker offers odds of +110 (decimal 2.10) on that team. The EV calculation for a $100 bet would be: (0.55 x $110) - (0.45 x $100) = $60.50 - $45.00 = +$15.50. This means that, on average, you would expect to profit $15.50 for every $100 wagered on this type of bet over the long run. Even though you will lose 45% of the time, the payout when you win more than compensates for those losses.

Key Points

• Foundation of profitable betting: Every successful long-term betting strategy is built on identifying and exploiting positive expected value opportunities.
• Requires accurate probability estimates: The usefulness of an EV calculation depends entirely on how well you estimate the true probability of each outcome.
• Short-term results may differ: A single bet or even a series of bets can produce results that diverge significantly from the expected value due to variance.
• The bookmaker’s edge is built-in: Most bets offered by sportsbooks have a negative expected value for the bettor because the odds include a margin (vig) that favors the house.
• Comparison tool: EV allows bettors to compare the quality of different wagers on a common scale, regardless of the sport, bet type, or odds format involved.