What Is Expected Value (EV) in Sports Betting?
Imagine two friends betting $100 on the Buffalo Bills to win an NFL game. One gets odds of +110, while the other finds +150 at a different sportsbook. Buffalo wins, so both friends celebrate, but one walks away with $40 more profit despite making exactly the same prediction.
Simply put, picking winners is important, but getting the right price matters just as much. Expected value measures the theoretical average profit or loss of a wager based on its potential payout and the probability of winning.
A bet with positive expected value (+EV) offers a favorable price, while a negative-EV bet doesn’t pay enough to justify the risk. And here’s something worth remembering throughout the article, that a losing bet can still have been a good decision.
How Does Expected Value Work?
Let’s start with something simpler than sports betting. Imagine I offer you a coin-flipping game where you pay $10 to play. If the coin lands on heads, you win $20 in profit. If it lands on tails, you lose your $10.
Would you accept? Mathematically, it’s a good deal. A fair coin gives you a 50% chance of winning $20 and a 50% chance of losing $10. If you played 100 times, you’d expect approximately 50 wins and 50 losses, leaving you with $500 in profit.
That works out to an expected profit of $5 per flip. You might lose the first five flips, but the underlying mathematics wouldn’t change. Sports betting follows the same principle, except that estimating the probability of a team winning is considerably harder.
Calculating EV on an NFL Bet
Suppose the Bills are playing the Kansas City Chiefs, and you find Buffalo at +150 odds. A $100 bet would earn $150 in profit if the Bills win, while a loss would cost you your original $100.
Those odds imply a 40% chance of winning, but after assessing the matchup, you believe Buffalo’s actual chances are closer to 45%.
- To calculate expected value, use that EV = (Win probability × Potential profit) − (Loss probability × Stake)
- For our example that would mean that EV = (0.45 × $150) − (0.55 × $100) = +$12.50
The wager has an estimated expected value of $12.50 per $100 bet, or +12.5%. You won’t actually receive $12.50 when the game finishes. You’ll either win $150 or lose $100. The figure represents your theoretical average profit across many comparable wagers, assuming your probability estimate is accurate.
What Makes a Bet Positive or Negative EV?
Every set of betting odds has a break-even probability, which tells you how often a wager needs to win to avoid losing money over time.
| American odds | Break-even probability |
|---|---|
| +200 | 33.3% |
| +150 | 40.0% |
| +100 | 50.0% |
| -110 | 52.4% |
| -150 | 60.0% |
| -200 | 66.7% |
If you believe a team has a 45% chance of winning and the sportsbook offers +150, you’ve potentially found positive EV because the break-even probability is only 40%.
But if you estimate its chances at 35%, the same wager has negative expected value. This is why backing a heavy favorite isn’t automatically a sensible choice, and betting on an underdog isn’t necessarily a gamble with poor value. What matters is the relationship between the odds and the likelihood of winning.
Why comparing Sportsbook Odds Matters
Here’s where EV becomes useful even if you don’t build statistical models or spend hours analyzing games.
Let’s say you want to bet $100 on the New York Rangers to win an NHL game. You estimate their chances at 48% and compare the available odds at five sportsbooks.
| Sportsbook | Example odds | Expected value on $100 |
|---|---|---|
| BetMGM | +110 | +$0.80 |
| FanDuel | +115 | +$3.20 |
| Fanatics | +120 | +$5.60 |
| Caesars | +105 | -$1.60 |
| BetRivers | +110 | +$0.80 |
Notice how the same wager goes from negative EV at +105 to positive EV at +120. Nothing about the Rangers or their opponent has changed. You’re simply getting a better return for taking exactly the same risk.
This is one of the easiest lessons to apply in practice. You might not know whether the Rangers have a 47%, 48% or 49% chance of winning, but you can avoid accepting +105 when another sportsbook offers +120 on the same market under the same rules.
How Do You Find Positive-EV Bets?
Finding a better price is relatively straightforward. Knowing whether it actually represents positive expected value is harder, because you need a reliable estimate of the outcome’s probability.
One approach is to compare odds across several sportsbooks. If four operators have the Boston Celtics at -140 while a fifth offers -115, that difference is worth investigating. Perhaps one sportsbook hasn’t fully reacted to new information, or the others are pricing the game more aggressively. Either way, it’s a starting point for research rather than proof of a profitable opportunity.
It also helps to understand what moves the odds. A starting pitcher change in MLB, an injured quarterback in the NFL or an unexpected NBA lineup can all affect a team’s chances. The important question is whether the sportsbook has already accounted for that information.
More experienced bettors sometimes track closing line value (CLV). Suppose you back an NBA team at +120, but the best available odds have dropped to +105 by tipoff. You secured a better price than bettors entering the market later. Consistently beating competitive closing odds can be a useful sign that you’re finding value, although it doesn’t guarantee profitability.
Remember that sportsbooks also build a margin, known as the vig, into their odds. That means the implied probabilities aren’t necessarily the true probabilities of the outcomes.
Does Positive EV Guarantee You’ll Win?
No since even a wager with a genuine 55% chance of winning still loses 45% of the time, and several losses can easily occur in a row.
There’s also the possibility that your probability estimate is wrong. Remember our Bills example? We calculated +12.5% EV because we estimated their chance of winning at 45%. If their actual chance were only 35%, the expected value would instead be -$12.50 per $100 wagered.
That’s the biggest challenge with EV betting. The formula is simple, but the result is only as reliable as the probabilities you put into it. This is also why bankroll management matters, even when you believe you’ve found an advantage.
Is Expected Value Worth Using?
We think so, and you don’t need to calculate EV for every wager to benefit from understanding it. The biggest advantage is that it changes how you approach betting.
Instead of simply wondering whether the Yankees will win tonight, you start thinking about whether the odds justify backing them. Rather than automatically using the sportsbook where you already have money deposited, you check whether another operator offers a better price.
That’s ultimately what expected value teaches you. Sports betting isn’t just about predicting what will happen. It’s about understanding how much you’re being paid for the possibility of being right.
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About the author
Senior Sports Betting Analyst
Dan Anderson is a Senior Sports Betting Analyst at Livesportsontv.com, specializing in NFL odds, bankroll management, and sportsbook promotions with over a decade of industry experience.