Expected Value Calculator: Find a Bet's EV

An expected value calculator tells you the average amount a bet wins or loses per dollar over the long run, so a price of +110 that should be −105 reads as a clear positive number. Expected value, or EV, is the single number that separates a bet worth taking from one that is not: feed it the odds and your estimate of how often the bet wins, and it returns the edge. Calculate the EV of any line with the tool below, then read on for the formula, a worked example, and the one input that decides whether the answer means anything.

Try It: Expected Value Calculator

Set a fair, sharp reference line on the left, then read the EV at each book on the right. The tool devigs the reference price into a true probability, compares it against every book's odds, and shows the expected value as a percentage. A green number is a positive EV bet. A red one means the price pays less than the outcome is worth.

The widget reports EV as a percentage of your stake. To turn that into a dollar figure for a specific wager, the expected value calculator takes a stake, the odds, and a win probability and returns the EV in dollars. Both answer the same question with the same math. Everything below shows you how it works.

What Expected Value Means

Expected value is the average result of a bet if you could place it thousands of times. Each time the bet wins you collect the profit, each time it loses you forfeit the stake, and EV weights those two outcomes by how often each one happens. The result is one number: the average profit or loss per bet.

A positive EV bet pays more than its true probability says it should, so it comes out ahead on average over a large sample. A negative EV bet pays less, so it bleeds money over the same sample. That is the entire game. You are not trying to win the next bet, you are trying to place bets whose average outcome is positive and let volume do the work.

The word average is load bearing. EV describes the long run, not the next result. A +5% EV bet can and often will lose on any given night, and a −5% bet can win. The edge only shows up across a large number of wagers.

The Expected Value Formula

EV starts from two inputs: the decimal odds the book offers and your own estimate of the win probability. Written per dollar of stake, the formula is:

$EV = p \cdot (o - 1) - (1 - p)$

Here p is your estimated win probability as a decimal and o is the decimal odds. The first term is the profit when the bet wins, weighted by how often it wins. The second is the stake you lose the rest of the time. Subtract the losses from the wins and you have the expected value per dollar.

To read it as a dollar figure, multiply by your stake:

$EV_\$ = \big[\, p \cdot (o - 1) - (1 - p) \,\big] \cdot \text{stake}$

The percentage form and the dollar form are the same calculation. The percentage tells you the quality of the price, and the stake scales it into money.

Worked Example: A +EV Bet

Take a line of +110, which is decimal 2.10. The price itself implies a break-even win rate of 1 / 2.10 = 47.6%, so the bet only needs to win 47.6% of the time to be fair. Suppose your own read, from a devigged sharp line, is that it actually wins 50% of the time.

Plug both into the formula per $100 staked:

EV = 0.50 × (2.10 − 1) − (1 − 0.50)
   = 0.50 × 1.10 − 0.50
   = 0.55 − 0.50
   = +0.05 per dollar

That is +5% EV, or +$5 on a $100 bet. The 2.4 point gap between the 47.6% the price implies and the 50% you project is the edge, and EV is what that gap is worth. Flip your estimate to 46% and the same price turns negative, which is the point: the number lives or dies on the probability you feed it. This example is illustrative, and any single bet at +5% EV can still lose.

Where the Win Probability Comes From

An expected value calculator is only as good as the win probability you put in. The odds are a fact printed on the screen. The probability is an estimate, and getting it wrong is the fastest way to turn a losing bet into one that looks profitable on paper.

The reliable way to estimate it is to read it off a sharp market rather than guess. A sharp book like Pinnacle prices efficiently, but its posted odds still bake in a margin called the vig, so you cannot use them raw. Strip the vig out first and the fair probability is what remains. A no vig calculator does exactly that, scaling both sides of a market back to a clean 100%, and the devigging guide covers which method to use when.

Two more pieces make the inputs precise. Every price is a probability in disguise, so an implied probability calculator turns any line into the percentage it bakes in, and the betting odds converter moves between American, decimal, and fractional so the format never trips you up. Get the fair probability right and the EV number means something. Guess at it and the calculator just launders a hunch.

Modeling Long-Run Returns

A single EV figure is a snapshot. To see what a persistent edge looks like across many bets, the model below compounds a fixed EV over a run of wagers. It is a theoretical projection, not a prediction of your results, and it assumes the edge holds and the bets are independent.

Notice how small a per bet edge can be and still add up. A 3% edge is modest, well below the 5% in the worked example, yet repeated over hundreds of bets it moves the needle. It also swings hard in the short run. Variance means a real bankroll rides a bumpy line around that average, and a bad stretch can wipe out weeks of edge before it recovers. Sizing each bet sensibly is what keeps you in the game long enough for the average to show up.

From One Bet to a Strategy

Calculating the EV of a single line is the foundation. Turning it into a repeatable process, scanning hundreds of markets for prices that beat their fair probability, is positive expected value betting, and it is where the calculator becomes a strategy rather than a party trick.

Two ideas carry it further. Closing line value checks your work after the fact: if the price you took consistently beats the market's closing number, your probability estimates are sound and the EV was real. And doing the scan fast enough to act before a price moves is a job for software, which is why bettors reach for the best EV betting tools once they are placing more than a handful of bets a day. The math stays the same. Only the speed and the scale change.

Frequently Asked Questions

How do you calculate expected value in betting?

Multiply your win probability by the profit if the bet wins, then subtract the chance of losing times the stake. In formula form, EV equals p times (o minus 1) minus (1 minus p), where p is the win probability as a decimal and o is the decimal odds. A price of 2.10 with a 50% win probability gives 0.50 times 1.10 minus 0.50, which is +0.05, or +5% EV.

What is a good EV in betting?

Any positive EV bet has a long-run edge, and in practice edges are small. A steady flow of bets in the +1% to +5% range is strong, and anything above that is rare and usually fleeting. The size of the edge matters less than placing positive EV bets consistently, because volume is what lets the average play out. A single high EV bet can still lose.

Is expected value the same as profit?

No. Expected value is the average outcome per bet over the long run, not the result of any one bet or a guarantee of profit. A positive EV bet loses often, and a run of them can lose money over a short sample before the edge shows. EV describes the tendency across many wagers, so it only translates into realized profit given a large sample and honest inputs.

What is a positive EV bet?

A positive EV bet is one where the odds pay more than the true probability of the outcome justifies. It happens when your estimate of the win chance is higher than the break-even rate the price implies. For example, a line implying 47.6% that you believe wins 50% of the time is positive EV. The gap between your probability and the price is the edge.

Can you use an EV calculator for parlays?

Yes, by multiplying the individual win probabilities and the individual decimal odds into a single combined probability and price, then running those through the same formula. The catch is that parlay EV compounds any error in each leg's probability, so a small mistake on one leg distorts the whole ticket. Accurate leg by leg probabilities matter even more than they do on a single bet.

Calculate Your Edge

Working out one bet's EV by hand takes a minute. Reading it on every price across every book, fast enough to bet before the number moves, does not. That is what the expected value calculator is for: enter a stake, the odds, and your win probability, and it returns the EV in dollars so you know whether a bet is worth taking before you place it.