What Is Expected Value (EV) in Sports Betting?

Value betting, +EV betting, and expected value all describe the same simple idea: only make a bet when the price pays you more than the bet deserves. If those words are new to you, that's okay. Most bettors have never heard them, and it usually means they're betting without an edge. This post explains it with one example, no math degree needed.

First, how odds work

Odds tell you how much a bet pays.

• +105 means a $100 bet wins $105.
• -110 means you bet $110 to win $100.

The bigger the payout for the same bet, the better the price for you.

The same bet has different prices

Here is one player prop: will a player get more or fewer than 8.5 rebounds? Four sportsbooks offer it, and they don't agree on the price.

The best over is +105 at Book C. The best under is +100 at Book A. You'd never pay $5 for milk when the store next door sells it for $4. Betting works the same way, and comparing prices across books is called line shopping.

Why a small price difference matters

Say the over really is a coin flip: 50/50. The fair price for a coin flip is even money, +100. Now make that bet 100 times at $100 each. You win 50 and lose 50 no matter which book you use. Only the price changes.

• At +105 you win 50 × $105 and lose 50 × $100: up $250.
• At -110 you win 50 × $90.91 and lose 50 × $100: down $455.

Same bets, same luck. That gap is what expected value means: the average you win or lose per bet if you made it over and over. A bet that comes out ahead on average is +EV. One that comes out behind is -EV.

The best price is not automatically +EV

This is where most people get it wrong. Getting the best price only means you beat the other books. It doesn't mean you beat the real odds.

If every book prices a bet around -150 and the best you can find is -140, you still need to win 58.3% of the time to break even. If the bet really wins 55% of the time, you lose about $5.71 per $100, best price or not. A bet is +EV only when its price beats the fair price.

So what is the fair price?

Nobody knows the true odds of a player getting 9 rebounds. Every fair price is an estimate, so the real question is how good the estimate is.

The way to find out is to track results. We have recorded hundreds of thousands of graded props across sportsbooks, and two patterns show up:

1. Some sportsbooks are more accurate than others. Their prices land closer to what actually happens.
2. Some kinds of bets do better than others. For example, overs and unders don't perform the same on player props.

Put those together and you get a better fair price: lean on the books with the best track record, and adjust for which side tends to hit.

In our example the blended fair price for the over is +100, a 50% chance. Book C pays +105, which beats it, so that's a +EV bet worth about $2.50 per $100.

You only know it works if you track it

An estimate is just a guess until it's tested. If a fair price is right, the bets that beat it make money over hundreds and thousands of plays. If it's wrong, they don't, and no single win or loss tells you which.

That's why SickFade grades every pick publicly, model by model, including the ones that lose. The app runs several strategies, each with its own record, so you can judge them yourself on the results page instead of taking anyone's word for it.

The one exception: arbitrage

There is one case where you don't need a fair price at all. Sometimes two books disagree so much that you can bet both sides and come out ahead whichever way it goes.

Bet $100 on the over at +110 and $100 on the under at +105. If it goes over you're up $10. If it goes under you're up $5. That's an arbitrage. They are rare, they close fast, and books can void bets or limit accounts that take them, so they're a bonus, not a plan.

When books post different lines

Books also disagree on the line itself, not just the price. One might post 8.5 rebounds while another posts 9.5.

Take the over 8.5 at one book and the under 9.5 at another, $110 each at -110. If he gets exactly 9 rebounds, both bets win and you're up $200. Any other number, one wins and one loses, and you're down $10. That's called a middle. It's a long shot by design, but it shows why the line matters as much as the price.

Losing stretches are normal

Even good bets lose. A 5% edge at -110 still loses about 45% of the time, and runs of 8 or 10 losses in a row happen over a season. The edge shows up over thousands of bets, not one weekend. Bet amounts you're comfortable losing, and judge results on a big sample.

Key takeaways

1. Expected value is what a bet wins or loses on average if you made it many times.
2. Line shopping gets you the best price, but the best price is not automatically +EV.
3. A bet is +EV when its price beats the fair price. The fair price is an estimate.
4. Tracking results is how you know whether an estimate is any good. Arbitrage is the only exception.
5. Losing streaks are part of it. Judge any approach on thousands of bets.