What is an EV calculator?
An EV (expected value) calculator tells you what a bet is worth on average: how much you would make or lose per bet if you placed it many times at the same price and the same true chance of winning. Positive EV means the price pays more than the true chance justifies; negative EV means you are paying the book's margin. This calculator works it out in dollars and as a percentage of your stake, and projects it over as many similar bets as you like.
How to calculate expected value in betting
EV = (win probability x profit if it wins) - (loss probability x stake). Example: $100 at +150 with a 43% chance to win. A win pays $150 profit, so EV = 0.43 x $150 - 0.57 x $100 = +$7.50 per bet, or +7.50% of the stake. The shortcut is EV % = decimal odds x win probability - 1 (2.5 x 0.43 - 1 = +7.50%). Over 100 bets like it, the expected result is +$750.00, with a typical swing of about $1237.69 either way, which is why a single result says little about whether a bet was good.
| Odds | Win probability | Break-even | EV per $100 | EV % | Over 100 bets |
|---|---|---|---|---|---|
| -110 | 55% | 52.38% | +$5.00 | +5% | +$500.00 |
| +100 | 50% | 50% | $0.00 | 0% | $0.00 |
| +150 | 43% | 40% | +$7.50 | +7.50% | +$750.00 |
| +200 | 30% | 33.33% | -$10.00 | -10% | -$1000.00 |
| +300 | 27% | 25% | +$8.00 | +8% | +$800.00 |
| -200 | 65% | 66.67% | -$2.50 | -2.50% | -$250.00 |
Where does the win probability come from?
The whole answer depends on it, so the calculator gives you three honest ways in:
- Both sides of a sharp line. Enter both prices from a sharp reference book. The calculator removes the vig proportionally (each side's implied probability divided by the total) and uses your side's fair probability. This is how most +EV bettors work: they compare one book's price with another book's fair price.
- A fair price. If you already have a fair, no-vig price (from our no-vig calculator or the +EV board), enter it directly.
- Your own win %. Your estimate from your own model or handicapping. Be honest here: EV is only as good as the probability behind it.
EV vs the Kelly criterion
EV tells you whether a bet is worth making and how much it is worth on average. It does not tell you how much to bet. For sizing, take the same price and probability to the Kelly criterion calculator, which turns your edge into a bankroll fraction (most bettors use a fraction of full Kelly to cut variance).
Why expected value matters more than any single result
A +EV bet still loses often: a 43% bet loses 57% of the time. What makes it worth placing is the price. Over hundreds of bets, results drift toward the expected value, and the typical swing grows more slowly than the expected profit, so a real edge shows up with volume. That is also why tracking your bets against the closing line (closing line value) is a faster read on your edge than your win-loss record.
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Frequently asked questions
What is a good EV percentage in sports betting?
Anything above zero is a positive expected value bet. Most real edges at US books are small, roughly 1% to 5% of the stake, and anything far above that is usually a stale or mistaken price or an overconfident probability estimate. Check the inputs before you trust a big number.
How do you calculate EV on a bet?
EV = win probability x profit if it wins - loss probability x stake. Or as a percentage: decimal odds x win probability - 1. A $100 bet at +150 with a 43% chance: 0.43 x 150 - 0.57 x 100 = +$7.50, which is +7.5% of the stake.
What is the difference between EV and the Kelly criterion?
EV measures how much a bet is worth on average. Kelly uses the same edge to decide how much of your bankroll to stake. Find the EV here, then size it with the Kelly criterion calculator.
Where should my win probability come from?
The most reliable source for most bettors is a sharp market: enter both sides of a sharp book's line and the calculator removes the vig to get a fair probability. You can also enter a fair price directly, or your own estimate if you have a model.
Is an estimated value calculator the same thing?
Yes. Estimated value and expected value calculators both answer what a bet is worth on average at a given price and win probability.
Is this calculator a Wise Guy Team pick?
No. It is math on the numbers you enter and makes no prediction. Our documented plays are posted separately, and every one is tracked win or loss.
21+ (or the legal age where you live). Gambling problem? Call 1-800-GAMBLER. This calculator does arithmetic on numbers you enter; it is not betting advice and not a Wise Guy Team play. Sportsbooks set their own bonus terms, limits and eligibility, so read the offer terms before you bet. Wise Guy Team is not a sportsbook and does not accept wagers. See our responsible gambling page.