Tool · Positive-EV betting
EV betting calculator: expected value of a bet
Calculate the expected value of a bet from the odds and a probability you trust, or from a reference market with the vig removed. Includes the EV formula.
Reviewed by Owen DavidsUpdated Oct 30, 2026Facts checked Oct 30, 2026
On this page
An EV betting calculator shows what a bet is worth on average: the expected profit per bet, given the odds and a win probability you trust. Enter the price and either your own probability or a reference market, and it compares your probability with the break-even rate the price implies.
Expected value (EV) calculator
- Expected value
- +$5.00
- +5.00% of stake
- Probability used
- 50.0%
- No-vig, from the reference market
- Break-even probability
- 47.6%
- Needed for this price to break even
- If it wins / loses
- +$110.00 / −$100.00
Assumptions and limitations
- EV = probability × decimal odds − 1, per unit staked. Equivalently, p × profit if it wins − (1 − p) × stake.
- The reference-market option removes the margin by proportional normalization. The answer is only as good as that market: a slow or low-limit line can make an edge look bigger or smaller than it is.
- Expected value is a long-run average over many similar bets, not a prediction for this one.
- Nothing you enter is stored or sent anywhere.
The expected value formula
Expected value (EV) is what a bet is worth on average, if you could place it many times at the same price and the same true probability.
EV = (probability of winning × profit if it wins) − (probability of losing × stake)
With decimal odds d and win probability p, that simplifies to:
EV per unit staked = p × d − 1
A positive result is a +EV bet; negative means the price doesn't pay enough for the risk.
A worked example
You can bet $100 at +110 (decimal 2.10), and you believe the outcome is a true 50/50.
| Value | |
|---|---|
| Profit if it wins | $110 |
| Loss if it loses | $100 |
| EV | 0.50 × $110 − 0.50 × $100 = +$5.00 |
| EV per unit | 0.50 × 2.10 − 1 = +5% |
| Break-even probability | 1 ÷ 2.10 = 47.6% |
The break-even probability is the win rate at which this price would be exactly fair. Your 50% is 2.4 points above it, which is where the +5% comes from.
The same bet at -110 (decimal 1.909) would need about a 52.4% win rate just to break even. At 50% it's a −4.5% bet.
Where the EV betting calculator's probability comes from
The formula is simple; the probability is the hard part. The calculator offers two ways to supply it:
- A reference market. Enter both sides of a market you consider sharp, and the calculator removes that sportsbook's margin to get a fair probability. See Implied probability and no-vig odds, explained for how that works and its limits.
- Your own estimate, for example from a model. Be honest about how uncertain it is.
For the bigger picture of how +EV bettors find and use these edges, see What is positive expected value (+EV) betting?.
Deciding how much to stake on a +EV bet is a separate question: see the Kelly calculator.Frequently asked questions
How do you calculate expected value in sports betting?
Multiply your win probability by the decimal odds and subtract 1. That's the expected profit per unit staked. For example, 50% at decimal 2.10 gives 0.50 × 2.10 − 1 = +5%.
What does +EV mean?
A positive expected value: at your probability, the price pays more than the risk is worth, so the bet makes money on average over many repetitions. It can still lose on any single bet.
Where do I get the true probability?
Usually from a sharp reference market with the margin removed, or from your own model. The calculator can remove the margin from a two-way market for you.
What is a break-even probability?
The win rate at which a price is exactly fair: 1 divided by the decimal odds. At -110 (1.909) it is about 52.4%.
About this page
- Editorial review
- Approved by Owen Davids on Oct 30, 2026
- AI assistance
- Drafted with AI assistance. Facts, sources and conclusions were checked by a human editor before publication.
- Facts last checked
- Oct 30, 2026
How we research and label evidence: our methodology.
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