Expected Value Calculator
Find out whether a bet is genuinely worth taking
⚖️ Step 1 — Get a fair probability
Enter both sides of a two-way market from a sharp book. This strips out the vig and gives you a true probability to work from.
What expected value means
Expected value is what a bet is worth on average if you could make it a thousand times. Positive EV means the price is better than the outcome deserves. Negative EV means it isn't.
It has nothing to do with whether a particular bet wins. A +EV bet loses all the time. The point is that if you consistently take prices better than the true probability, the arithmetic works out over a season regardless of any single result.
The formula: EV = (probability of winning × profit if you win) − (probability of losing × amount risked)
At -110 risking $100, you profit $90.91 if right and lose $100 if wrong. If your true win probability is 55%: (0.55 × $90.91) − (0.45 × $100) = +$5.00 per $100 bet.
The hard part isn't the math — it's step 3
Anyone can run the formula. The entire difficulty of betting sits in estimating that win probability better than the market does.
Here's the trap: if you use the book's own implied probability as your estimate, you'll always get slightly negative EV. That's the vig, and it's baked in by design. To find a genuine edge, your probability has to come from somewhere other than the price you're evaluating.
Where a defensible number comes from
- A sharper book's no-vig line. If Pinnacle or Circa prices something at a fair 54% and your book is offering a price implying 51%, that's a real 3-point edge. The no-vig tool above does this conversion.
- A model. Your own projections, power ratings, or whatever you've built.
- Information the market hasn't absorbed. Injury news, a lineup change, weather — but only if you're genuinely early.
"I think this team looks good" is not an estimate. If you can't say where a number came from, the calculator will happily confirm a bet that isn't there.
Why the no-vig step matters
A two-way market priced -110/-110 implies 52.38% on each side — 104.76% total. That extra 4.76% is the sportsbook's hold. It can't be a real probability distribution, because probabilities sum to 100%.
Removing the vig means scaling both sides back proportionally so they add to 100. In the -110/-110 case, both sides come out at a fair 50%. Now you're comparing against a real number rather than a padded one.
What size edge is realistic
Sustained edges of 2–4% are strong. Bettors who consistently find 5%+ tend to get limited quickly.
If the calculator tells you a bet has a 15% edge, the overwhelmingly likely explanation is that your probability estimate is wrong — or the line is stale for a reason you don't know yet. Very large edges on liquid markets are usually a signal that you're missing information, not that you've found a gift.
Common questions
What is expected value in sports betting?
Expected value is the average amount a bet would return per attempt across a large number of identical bets. A positive EV bet is priced better than the true probability of the outcome; a negative EV bet is priced worse. It's calculated as (win probability × profit if won) minus (loss probability × amount risked).
How do I estimate the true win probability?
The most practical method is taking a sharp book's two-way market and removing the vig, which produces a fair probability you can compare against softer prices elsewhere. Alternatives are your own model or genuinely early information. Using the same book's implied probability will always show negative EV because the vig is built in.
What does removing the vig mean?
Sportsbook odds on a two-way market sum to more than 100% implied probability — the excess is the hold. Removing the vig scales both sides proportionally so they total 100%, giving the book's actual estimate of each outcome without its margin.
Does a positive EV bet mean I'll win?
No. A +EV bet can lose, and often will. Expected value describes the long-run average across many bets, not the outcome of any single one. A bet with a 4% edge at -110 still loses roughly 45% of the time.
What's a good edge to look for?
Sustained edges of 2 to 4 percent are considered strong. Edges much larger than that on liquid markets usually indicate either a flawed probability estimate or information you don't have yet, rather than genuine value.
More Free Tools
If you or someone you know has a gambling problem, call 1-800-GAMBLER
Powered by Bettor Day