Is the price worth it?
EV Calculator
Enter the odds you can get and your best estimate of the true win probability — your own number, vig-free fair odds, or a sharp market.
Long-run average, not a prediction of this bet. Win-or-lose bets only: no pushes, commission or promos.
Transparent math
How the EV formula works
Expected value compares the price you are getting with how often the bet should win. Everything else on this page follows from one line.
Read our methodology →expected profit = S × EV
break-even probability = 1 ÷ D (× 100 for %)
probability edge = (p − 1 ÷ D) × 100 percentage points
fair decimal odds = 1 ÷ p · full Kelly = EV ÷ (D − 1)
Example: $100 at +150, 45% true win chance
- Decimal odds 2.50, so break-even is 40.00%
- EV = 0.45 × 2.50 − 1 = 12.50%, expected profit $12.50
- Fair odds for a 45% shot are exactly 11/9 fractional (decimal 2.222…, about +122 American) — any price longer than the exact fair price is +EV; the rounded American figure is only a guide
The hard part
Where the win probability comes from
The formula is exact; the probability is not. The calculator accepts three kinds of estimate, and each one is only as good as its source.
Fair odds: a price that already has the bookmaker margin removed.
Sharp market: every outcome of a low-margin market; the margin is removed proportionally.
Sharp market examples
- −110 / −110 has a 4.76% margin; removing it leaves 50.00% per side, so +105 elsewhere is 2.50% EV ($2.50 per $100)
- Betting the same side at the sharp book's own −110 is −4.55% EV — your expected loss per unit staked, if the no-vig estimate is right (the bookmaker's expected take is the mirror image, 4.55%). It is not the same number as the 4.76% margin: EV at the book's own price is 1 ÷ (1 + margin) − 1
- Three-way soccer market 2.10 / 3.40 / 3.80 (margin 3.35%): the away side's fair chance is 25.46%, so 4.20 at another book is 6.95% EV
- A raw price is not a fair price: −110 implies 52.38%, but with the margin removed that side is 50.00%. Typing a raw line into “Fair odds” overstates the win probability — enter the whole market instead
Two different numbers
EV % vs probability edge
Both measure an edge, but on different scales. Mixing them up makes a bet look better or worse than it is.
EV = probability edge × decimal odds = 12.50% of the stake
Why it matters
- EV % is return per unit staked — the number to compare bets with
- Probability edge is how far your estimate sits above break-even — useful for judging how wrong your estimate can be before the bet turns −EV
- Full Kelly here is 8.33% of bankroll; staking a fraction of that reduces the swings — see the Kelly calculator
Read the fine print
What this calculator assumes
The math covers a plain cash bet that wins in full or loses in full. Real bets often have extra outcomes that change the answer.
Outside the model
- Pushes and voids — whole-number spreads and totals, cancelled games
- Half-win / half-loss Asian handicap lines
- Exchange commission (see the matched betting calculator)
- Boosts and free bets (see the profit boost calculator)
A positive EV is never a guarantee for a single bet. If betting stops being fun, see our responsible gambling page.
Learn the math
Guides that go with this calculator.
What Is Vig in Betting?
What is vig in betting? How vigorish works, with a −110/−110 example: 4.76% margin, 4.55% theoretica…
Kelly Criterion: How to Size Bets Using Your Edge
Learn the Kelly criterion with real numbers: a 55% win chance at evens gives a 10.00% full Kelly sta…
EV Betting: A Plain-English Guide to Positive EV
Learn EV betting with a worked example: a +150 bet at a 45% win chance has 12.50% EV and $12.50 expe…
FAQ
Frequently asked questions
What is expected value (EV) in betting?
EV is what a bet returns on average if you could place it many times at the same price and the same true chance of winning. The formula is EV = win probability × decimal odds − 1. A $100 bet at +150 (decimal 2.50) that really wins 45% of the time has an EV of 12.50% — an expected profit of $12.50 per bet, even though each single bet either wins $150.00 or loses the stake.
What does +EV mean?
A positive-EV (+EV) bet is one where your win probability is higher than the break-even probability implied by the odds you are getting. At +150 you need to win 40.00% of the time just to break even; at a true 45.00% you are 5.00 percentage points above that line, which is what makes the bet +EV. If the two are equal — say even money at exactly 50% — EV is 0.00% and the bet is break-even.
Where does the "true" win probability come from?
It is always an estimate. You can type your own number, enter odds that already have the bookmaker margin removed (fair odds), or paste a sharp bookmaker's full market and let the calculator remove the margin proportionally. A −110 / −110 market strips down to 50.00% each side, so +105 elsewhere is 2.50% EV. The no-vig figure is the market's opinion, not a guarantee: if the sharp market is wrong, your EV is wrong too.
Does a positive EV bet guarantee a profit?
No. EV is a long-run average. The +150 example at 45% still loses 55% of the time; the $12.50 expected profit is an average, not a promise — even over many bets, results can fall short of it, and if your probability estimate is wrong, the edge is wrong too. Results swing far more than the edge, which is why stake sizing matters: the Kelly criterion calculator sizes stakes from the same edge, and fractional Kelly cuts the swings compared with full Kelly (quarter Kelly here would be $20.83 of a $1,000 bankroll).
What doesn’t this EV calculator model?
It assumes a simple cash bet that either wins in full or loses in full. Pushes and voids (whole-number spreads and totals), half-win/half-loss Asian handicap lines, exchange commission, free bets and boosts are not included. If a push is possible, true EV is win probability × decimal odds + push probability − 1, so entering only the win probability here understates the bet. For promos use the profit boost calculator or the free bet calculator.
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