01How to use the EV calculator
- Pick the odds format you're used to. Decimal is the default, but fractional and American work too.
- Choose how you want to give your view of the bet: as a probability, say 48%, or as fair odds, say 2.08.
- Enter the bookmaker's odds, the actual price you can get.
- Read the result. EV tells you what you'd make or lose per unit staked on average. Add a stake if you'd rather see it in units.
- Hit "Copy link" to save or share the calculation.
02The expected value formula
Expected value is the average result of a bet if you could place it many times under the same conditions. Per 1 unit staked:
EV = (probability x decimal odds) - 1Multiply by 100 for EV%. If you think in fair odds instead of probabilities, the fair odd is just 1 divided by the probability, so the same formula becomes:
EV% = (bookmaker odds / fair odds - 1) x 100The calculator also shows two related numbers:
Break-even probability = 1 / bookmaker odds
Edge (points) = (your probability - break-even probability) x 100Break-even probability is the chance the bet needs to win just to not lose money in the long run. Edge is how far your probability sits above that line. EV and edge usually point the same way, but they aren't the same thing: a 2 point edge is worth +4% at evens (52% at 2.00) and +20% at 10.00 (12% at 10.00). The longer the odds, the more each point of probability is worth, and the more a small mistake in your estimate costs you.
03Worked examples
Example
Example 1: a positive EV bet.
You think a player has a 48% chance to have a shot on target, and a bookmaker offers 2.30.
- EV = 0.48 x 2.30 - 1 = 0.104, so +10.4%.
- Break-even probability = 1 / 2.30 = 43.48%.
- Edge = 48.00 - 43.48 = +4.52 points.
- On a 10 unit stake, that's an expected profit of about +1.04 per bet. You still lose this bet more often than you win it (52% of the time). The profit only shows up over many bets.
Example
Example 2: a negative EV bet.
Your fair odds are 2.50 (a 40% chance) and the best price you can find is 2.20.
- EV% = (2.20 / 2.50 - 1) x 100 = -12%.
- Break-even probability = 1 / 2.20 = 45.45%, so you're 5.45 points short.
- You'd need 2.50 or bigger before this bet is worth it.
04Frequently asked questions
What is a good EV% in sports betting?
Most genuine edges are small, somewhere around +2% to +5%. Bigger numbers happen, but the bigger the EV, the more you should ask why the price is so generous. Often the bookmaker knows something, like a player who isn't starting, or your probability is off.
What's the difference between EV and edge?
Edge is the gap between your probability and the break-even probability, in percentage points. EV is what that gap is worth per unit staked. The same edge is worth more at longer odds, which is why long shots can show huge EV numbers from a small disagreement.
Where do I get my probability from?
Three common sources: the market itself (take a sharp price, remove the margin with the fair odds calculator and treat the result as the true chance), a model like JOPP's, or your own judgement. Whichever you use, the EV you get is only as good as that number.
Does positive EV mean I'll win?
No. EV is a long-run average. A single bet still wins or loses, and even a run of well-priced bets can lose for weeks. It's a way to judge prices, not a promise of profit.
Can I use fractional or American odds?
Yes. Switch the odds format at the top and type the odds as you see them, for example 13/10 or +130. The calculator converts everything to decimal behind the scenes.
Why is my EV different when I type fair odds instead of a probability?
Usually rounding. A 48% probability is a fair odd of 2.0833. If you type 2.08, the calculator uses 2.08, which gives +10.58% instead of +10.40% against odds of 2.30. Type more decimals if you want them to match exactly.