+EV betting

What is +EV betting?

+EV is short for positive expected value. +EV betting is the process of taking bets that have a positive expected value, meaning they will be profitable in the long run.

What is expected value?

Expected value is a basic term used in probability and statistics. It represents the expected long-term average of an event if it's repeated indefinitely.

The simplest example is a coin flip. There are two outcomes - heads and tails, both with a 50% chance of occurring. If you place a $10 bet that a coin will land heads, you will either lose $10 or profit $10. The expected value of this bet is calculated by taking each outcome's profit, multiplying it by the probability it happens, and adding the results together. For this example, that would be

(-$10 * .5) + ($10 * .5) = $0

Essentially, this represents the expected average profit if you keep placing this bet over and over.

How does this relate to sports betting?

Sports betting odds are just another way of representing probability. You can use an odds converter like this one to find the probability that the sportsbook is implying for a bet.

How does this help us place profitable bets?

Back to the coin flip. Using the odds converter you can see that 50% probability converts to +100 american odds. Because we know the true probabilities, +100 is considered "fair odds".

Now, let's say Fanduel is running a Super Bowl promotion where they are offering +120 odds on the coin flip. So now, instead of profiting $10 if you guess right, you profit $12. This changes the expected profit of the bet to

(-$10 * .5) + ($12 * .5) = $1

Now, on average you will profit $1 every time you place a $10 bet. Essentially, if a sportsbook is offering better odds than the fair odds, it is considered a profitable bet.

How to calculate fair odds in sports betting

So far, we've only discussed the simple example of flipping a coin, which has clear outcome probabilities. In sports betting, we can't predict the future, so we can't actually calculate the true probabilites of certain events occurring.

However, there are techniques we can use to estimate fair odds which allow us to be profitable in the long run.

Searching for outliers

Instead of trying to figure out what fair odds should be, we can let the sportsbooks do it for us. Essentially, each sportsbook has their own method of setting odds. Naturally, they don't always agree. If most sportsbooks are offering around -150 for the Bears to beat the Packers, but Draftkings is an outlier offering -110, that could be a strong case for a +EV bet.

Calculating fair odds (devigging)

As mentioned, we will rely on the sportsbooks to estimate what the fair odds should be. However, it's not as simple as using the odds that the book lists (e.g. -150 for Bears Moneyline).

All sportsbooks have some "vig" or "juice" built into their odds. Essentially, if a sportsbook determines that the fair odds for the Bears to win are -140, they will offer a slightly worse price of -150. This ensures that they make money and gives them some margin of error for setting odds.

Basically, we have to do the reverse and remove the vig ourselves to find the fair odds. That's why it's called devigging.

The easiest example to visualize this process is to look at spreads or totals for various sports, especially higher scoring sports like the NBA. The sportsbook will typically offer -110 for the over and -110 for the under. Since both outcomes have the same price, it's intuitive to say that the fair odds are likely +100/+100.

However, for most scenarios, precise devigging is less intuitive. If a book is offering -300 for the Dodgers Moneyline and +210 for the Cardinals, it's less clear. Fair odds could be anywhere between -300/+300 and -210/+210. This is where the math comes in.

There are a various mathematical methods that can be used to devig. The general consensus is that casual bettors tend to overbet on underdogs, and sportsbooks apply more vig to underdogs to compensate and limit risk on big games. EVantage uses the Power method to devig, which takes this bias into account. Using the power method to devig -300/+210 yields -260/+260 fair odds.

Calculating EV

This is the final step of the process. Let's go back to the Dodgers/Cardinals example. We found that fair odds are +260 for the Cardinals to win. Let's say you found a sportsbook that prices the Cardinals at +280. That's a +EV bet, but how much +EV is it? We will just use the same simple formula from the original coin flip example:

(win probability x profit) - (loss probability x stake)

Let's say you bet $100 on Cardinals which would be a profit of $280 if it wins. +260 converted is 27.8% and -260 converted is 72.2%.

(.278 * $280) - (.722 * $100) = $5.64 expected profit. This can also be represented as 5.64% EV since the wager was a clean $100.

Once you know the EV%, you can effectively use that value as an expected ROI. So wagering $10 would expect 56 cents of profit.

What EVantage shows

On each scanner result you will typically see:

  • Price — the best odds among your selected books for that outcome
  • EV% — expected value vs the power-method fair line
  • Fair odds — the estimated no-vig price (power)
  • Implied — win probability implied by the book’s price
  • Devig books — which books were used to build the fair line (and their weights)

Filters like Min Devig Books, Devig Book weights, and Min/Max Odds change how strong those signals are. Higher min books and heavier weight on sharp sources usually means a more trustworthy fair line.

Key takeaways

  • +EV means the book’s price is better than your estimate of fair value.
  • Fair value comes from removing vig from sharp(er) books, not from the soft book itself.
  • EV is a long-run expectation. Individual bets still win or lose.
  • The scanner finds candidates. You still decide whether the signal is good enough to bet — covered next in Trusting +EV signals.