EV betting means judging a bet by its expected value: what it would win or lose on average if you could make the same bet many times. In words, the formula is the chance of winning times the profit, minus the chance of losing times the stake.
A bet with a positive result is +EV, one with a negative result is -EV, and the whole method rests on one input you have to supply: the chance. The rest of this page works the sum on real and example prices, step by step.
What does EV mean in betting?
EV stands for expected value. On a $100 bet:
EV = (chance of winning x profit if it wins) – (chance of losing x $100)
The profit comes from the odds. At American odds of +120, a $100 bet wins $120. At -110, you stake $110 to win $100, so $100 wins $90.91. Our guide to how betting odds work converts any price.
EV is an average, not a forecast of one result. A single bet still either wins or loses.
A -EV bet at a normal price
Take a bet at -110 on a side with a 50% chance of winning. This is an example, not a game.
- Win: 0.50 x $90.91 = $45.45
- Lose: 0.50 x $100 = $50.00
- EV: $45.45 – $50.00 = -$4.55
Over many such bets you would lose about $4.55 for every $100 staked. To break even at -110 a bet has to win 110 / 210 of the time, or 52.38%.
A +EV bet
Now the same 50% chance at +120.
- Win: 0.50 x $120 = $60.00
- Lose: 0.50 x $100 = $50.00
- EV: $60.00 – $50.00 = +$10.00
At +120 the break-even rate is 100 / 220, or 45.45%. Any true chance above that makes the bet +EV. Everything depends on whether the 50% is right, and that number is never printed on the betting board.
Where the chance comes from: remove the margin first
A price states a chance: 100 divided by the decimal odds. But the two sides of a game add up to more than 100%, because the book builds its margin into both prices. To read the market’s own view, take the margin out.
A real price: DraftKings’ moneyline on Pittsburgh Steelers at Tampa Bay Buccaneers, Sunday, October 18, 2026, read through the Nucleus odds feed at 05:10 UTC on October 16.
| Pittsburgh | Tampa Bay | |
|---|---|---|
| DraftKings price | -147 (1.68) | +124 (2.24) |
| Chance the price states | 59.52% | 44.64% |
| With the margin removed | 57.14% | 42.86% |
The stated chances are 100 / 1.68 and 100 / 2.24. Together they come to 104.17%, so the margin is 4.17 points. Divide each by that total, working from the unrounded figures, and the pair adds up to 100%: 57.14% and 42.86%. Our page on calculating overrounds covers the same step, and the implied probability guide the conversion.
Now price each side against those no-margin chances. A $100 bet on Pittsburgh wins $68: 0.571429 x $68 – 0.428571 x $100 = -$4.00. A $100 bet on Tampa Bay wins $124: 0.428571 x $124 – 0.571429 x $100 = -$4.00. Against the book’s own fair line, both sides lose $4 per $100 on average. That is the margin, seen from the bettor’s side.
So a bet is only +EV if your chance is better than the market’s no-margin chance by more than the margin. That is a claim about the game, and it has to come from somewhere other than the price.
EV and the closing line
The closing line is the last price before the game starts. It makes a natural yardstick for EV: with the margin removed, the closing price is the market’s last estimate of the chance before the game.
If you took +120 and the closing line, margin removed, put that side at 50%, the bet you made was worth +$10 per $100 by that measure, whatever the score. Beating the closing line is a way of checking estimates after the fact. It does not settle any single bet. Our betting strategies guide explains why staking systems do not change EV, and arbitrage betting covers the rare case where the best prices at two books add up to less than 100%.
Why a +EV bet still loses often
Take the +EV example: $100 at +120 with a true 50% chance, worth +$10 a bet on average. The number of wins follows a binomial distribution, and the chance of being behind after a run of these bets is:
| Bets | Wins needed to be ahead | Chance of being behind |
|---|---|---|
| 1 | 1 | 50.00% |
| 10 | 5 | 37.70% |
| 100 | 46 | 18.41% |
After 100 such bets the expected profit is $1,000, yet nearly one run in five ends behind. A positive EV is a long-run figure, and the long run is longer than most people expect. Books can also limit accounts, as our page on why sportsbooks limit players explains.
None of this says a bettor or a method wins. EV is a way to price a bet once you have a chance you trust; it does not supply the chance.