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Expected Value (EV) Calculator
Expected Value (EV) Calculator
Is this bet actually worth making? Paste your odds, tell the calculator what the fair probability is (or let it strip the vig from a sharp book's line), and see your edge, your expected profit and the stake Kelly would recommend.
Use Pinnacle, Circa or the market consensus. The vig is removed with the multiplicative method.
What expected value means in betting
Expected value is the average result of a bet if you could place it thousands of times. A +EV bet makes money on average, even though any single one can lose. A −EV bet loses money on average, even though any single one can win. Every bet a sportsbook offers at face value is −EV by design, because the odds include a margin (the vig). Your job is to find the prices where the book, or the market, is wrong by more than that margin.
Think of it as the difference between the price you pay and the price the bet is worth. If the true chance of an outcome is 51% and your book pays you as if it were 48.8% (+105), you are being overpaid, and the surplus is your EV.
The EV formula, with a worked example
EV = (fair probability × profit if you win) − ((1 − fair probability) × stake)
Say Pinnacle prices a game at -115 / -105 and your book offers +105 on the -115 side. Removing the vig from Pinnacle's line (see below) gives a fair probability of 51.1% for your side. At +105, a $100 bet wins $105.
- Win branch: 0.511 × $105 = $53.66
- Lose branch: 0.489 × $100 = $48.92
- EV = +$4.72 per $100 bet, or +4.7%.
That is a strong edge. Most professional bettors work with edges of 1% to 3% and make it up on volume and discipline. The calculator above does the same math instantly and adds the Kelly stake.
How to find the fair probability
The whole calculation hinges on one input, and it is the one nobody can give you for free. Three ways to estimate it, from most to least reliable:
- De-vig a sharp book. Take both sides of the line at Pinnacle or Circa, convert to implied probabilities, and scale them so they add to 100%. For -115 / -105: implied 53.5% and 51.2%, total 104.7%, so the fair probabilities are 51.1% and 48.9%. This is the multiplicative method the calculator uses. It is not perfect (favorites tend to be slightly over-priced, the "favorite-longshot bias") but it is the industry standard.
- Use the closing line. The last price before kickoff at a sharp book is the best public estimate of the true probability. If you consistently bet at better prices than the close, you are +EV even before your results show it. This is called closing line value (CLV).
- Build a model. Power ratings, simulations, injury adjustments. This is what we do at Elite Bettings for the picks we publish; it is also the hardest and the easiest to fool yourself with. Always test a model's probabilities against the closing line before trusting it.
Kelly: how much to bet on a +EV play
The Kelly criterion gives the stake that maximizes long-term bankroll growth:
Kelly fraction = (fair probability × decimal odds − 1) ÷ (decimal odds − 1)
For the example above: (0.511 × 2.05 − 1) ÷ 1.05 = 4.5% of bankroll. On a $2,000 bankroll that is $90. Full Kelly is famously aggressive: a 20% error in your probability estimate can turn it into a bankroll-destroying stake. Almost every serious bettor uses a fraction, usually a quarter to a half. Quarter Kelly here is about $22, or roughly 1 unit if you size units at 1% of bankroll.
Two practical rules: never bet more than 3–5% of your bankroll on a single game whatever Kelly says, and recalculate your bankroll monthly, not after every bet.
Why +EV bettors still lose for weeks
A 3% edge on -110 bets means winning about 54% of the time. Over 100 bets the standard deviation of your win rate is about 5 points, so a "true 54%" bettor will post a losing 100-bet stretch roughly one time in three. Over 1,000 bets the standard deviation shrinks to 1.6 points and the edge becomes visible. This is why:
- Track closing line value, not just profit. CLV shows up in 50 bets; profit takes 500.
- Judge a picks service on sample size and CLV, not on a hot week. Ask for the tracked record.
- Stake so that a normal losing streak (8 to 10 losses in a row happens to a 54% bettor every season) does not cost more than 15% of your bankroll.
Five mistakes that turn +EV into −EV
- Comparing against your own book's other side. De-vigging a soft book's line only tells you that book's opinion. Use a sharp reference.
- Ignoring limits and line movement. If you found +EV on a big number, the line probably moves before your full stake is in.
- Betting stale lines after injury news. Books will void or limit you, and "free money" from a stale line is not a sustainable edge.
- Over-betting promos. Boosts and free bets are real EV, but the calculator has to include the promo's real payout, not the headline odds.
- Parlaying +EV legs at a book that reprices them. Some books price parlays with extra hold. Check the parlay's combined odds against the product of the singles with our parlay calculator.
FAQ
What is a good EV percentage for a sports bet?
Anything above 0% is technically worth betting. In practice, 1–3% edges are realistic and repeatable on main markets; 5%+ edges are common on player props and derivative markets, but limits are lower and lines move fast.
Is a +EV bet guaranteed to win?
No. EV describes the average over many bets. A +EV bet at +105 still loses about 49% of the time.
Which de-vig method does the calculator use?
The multiplicative (proportional) method: each implied probability is divided by the sum of both sides' implied probabilities. Power and Shin methods correct for favorite-longshot bias and give slightly different results on lopsided lines.
What is the break-even win rate at -110?
52.38%. At +100 it is 50%, at -120 it is 54.5%, at +150 it is 40%. The break-even rate is just the implied probability of the odds.
Should I use full Kelly?
Almost never. Quarter to half Kelly captures most of the growth with a fraction of the drawdowns, and protects you when your probability estimate is off.
Every Elite Bettings pick ships with its fair odds and edge
We publish NFL, NBA, MLB and NHL picks with the line we beat, the closing line value we expect, and a track record verified on a third-party tracker. No "locks", just +EV.
See today's picks21+ in most US states (18+ in DC, NH, RI, WY), 19+ in most Canadian provinces (18+ in AB, MB, QC). This calculator is for information only and does not guarantee results. Gambling problem? Call 1-800-GAMBLER (US) or 1-866-531-2600 (ConnexOntario).