Expected Value (EV)
The average you can expect to win or lose per bet over the long run.
Expected value, usually shortened to EV, is a stat that shows the average result of a bet if you made it over and over under the same conditions. You work it out by multiplying each possible outcome by its probability and adding those pieces together. A positive expected value (+EV) means a bet pays off over the long run, while a negative expected value (-EV) means you can expect to lose money over time. Pros and serious recreational bettors treat EV as the single most important way to judge whether a bet is worth making.
To get EV, you have to separate 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 that shows up across hundreds or thousands of bets. Bettors who keep finding and placing +EV bets will, over a big enough sample, come out ahead. Those who keep taking -EV bets will watch their bankroll shrink, no matter how good a short hot streak feels.
Example
Say you think a team has a 55% chance of winning, and the book offers +110 (decimal 2.10) on that team. The EV math for a $100 bet is: (0.55 x $110) - (0.45 x $100) = $60.50 - $45.00 = +$15.50. So on average, you’d expect to profit $15.50 for every $100 you bet on this kind of spot over the long run. Even though you lose 45% of the time, the payout when you win more than makes up for those losses.
Key Points
- Foundation of profitable betting: Every winning long-term strategy is built on spotting and cashing in on 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 even a run of bets can land far from the expected value because of variance.
- The bookmaker’s edge is built-in: Most bets the books offer are negative EV for you, since the odds include a margin (vig) that tilts things toward the house.
- Comparison tool: EV lets you stack up different bets on one scale, no matter the sport, bet type, or odds format.