Expected Value (EV)
The average profit or loss a bettor can expect per wager over the long run.
Expected value, almost always shortened to EV, is the statistical measure of what a bet returns on average if you ran it over and over under identical conditions. You calculate it by multiplying each possible outcome by its probability, then adding the products together. Positive expected value (+EV) means a bet is profitable over the long run; negative expected value (-EV) means you can expect to bleed money over time. Pros and serious recreational bettors treat EV as the single most important gauge of whether a wager is worth making.
The key to EV is separating one bet’s result from the math driving it. A +EV bet can still lose on any given night, and a -EV bet can still cash. What counts is the pattern that emerges across hundreds or thousands of wagers. Bettors who reliably find and fire +EV bets will, over a large enough sample, turn a profit. Those who keep taking -EV bets will watch their bankroll erode — short-term hot streaks notwithstanding.
Example
Say you put a team’s win chance at 55%, and the book offers +110 (decimal 2.10) on that team. The EV math on a $100 bet runs: (0.55 x $110) - (0.45 x $100) = $60.50 - $45.00 = +$15.50. Translation: on average, you’d expect to profit $15.50 for every $100 staked on this type of bet over the long run. You’ll lose 45% of the time, sure — but the payout when you win more than makes up for it.
Key Points
- Foundation of profitable betting: Every winning long-term strategy is built on spotting and exploiting positive expected value.
- Requires accurate probability estimates: An EV calculation is only as good as your read on the true probability of each outcome.
- Short-term results may differ: A single bet — or a whole run of them — can swing well clear of the expected value thanks to variance.
- The bookmaker’s edge is built-in: Most bets a sportsbook offers carry negative EV for the bettor, because the odds include a margin (vig) tilted toward the house.
- Comparison tool: EV lets you stack different wagers against each other on a common scale, no matter the sport, bet type, or odds format.