How to use the EV calculator
- Enter the odds you can bet at, in any format, and your stake.
- For the fair price, enter the odds of a sharp book on both sides of the market. The calculator removes the bookmaker's margin and uses the result as the fair chance.
- No sharp odds? Leave those two boxes empty and set your own win chance with the slider.
You see:
- Fair chance: the probability used for the calculation,
- Edge (ROI): expected profit as a percentage of the stake,
- EV per bet: expected profit in dollars,
- Fair odds: the odds at which the bet would be exactly break-even.
The maths
- Fair chance from a sharp market = (1 ÷ odds, same side) ÷ (1 ÷ odds, same side + 1 ÷ odds, other side).
- Edge = fair chance × decimal odds − 1.
- EV = stake × edge.
- Fair odds = 1 ÷ fair chance.
Worked example
A sportsbook offers 2.10 (+110) on a team. A sharp book has the same team at 1.95 and the other side at 1.95.
- The sharp market is 51.3% + 51.3% = 102.6%, so the margin is removed by dividing: the fair chance is 51.3% ÷ 102.6% = 50.0%.
- Edge = 0.50 × 2.10 − 1 = +5.0%.
- On a $20 stake the EV is +$1.00, and the fair odds are 2.00 (+100).
Using your own estimate instead, 55% at odds of 2.10 gives an edge of +15.5% and an EV of +$3.10 on $20. The difference between the two shows why the source of your probability matters more than the maths.
Tips
- Use a sharp reference. A low-margin book or a betting exchange is a better benchmark than a soft book's line.
- Check the timing. Odds move. A price that was +EV five minutes ago may not be now.
- Size by edge. The Kelly calculator turns an edge into a stake, and most bettors use a fraction of it.
- Track it. The closing line value calculator tells you whether your bets really had an edge.
To strip the margin out of a market with more than two outcomes, use the no-vig calculator. Read value betting for the full picture and bankroll management for staking. For esports lines, there is an esports expected value calculator.