Methodology
- Estimate your fair win probability from a model or no-vig market price.
- Convert the available American price to decimal odds and break-even probability.
- Compute EV in dollars and as a percentage of stake.
- Require a cushion above break-even before betting to absorb estimate error.
Break-even probability first
Every price has a break-even probability — the win rate you need just to not lose money. Before chasing edge, you should be able to state the break-even and your estimate gap above it.
- -110 needs ~52.38% to break even
- +100 needs 50% to break even
- +200 needs ~33.33% to break even
- -200 needs ~66.67% to break even
EV in dollars, not just percent
A 5% EV on a $20 bet is $1 of expected profit. The same 5% EV on a $200 bet is $10. Dollar EV scales with stake; percent EV compares estimates across different stake sizes. Neither predicts the result of a bet.
- Use dollar EV for ranking which plays move the needle
- Use percent EV for comparing plays of different sizes
- Require a minimum percent EV threshold to filter low-quality edges
- Pair every EV calculation with a Kelly sizing step before clicking
EV snapshot at $100 stake · Hypothetical example
Estimated win probability of 55% at each price; dollar EV rounded to cents.
| Price | Break-even | EV ($) |
|---|---|---|
| -110 at 55% fair | 52.38% | +$5.00 |
| -105 at 55% fair | 51.22% | +$7.38 |
| +100 at 55% fair | 50.00% | +$10.00 |
| +105 at 55% fair | 48.78% | +$12.75 |
At the same estimated 55% probability, -105 raises EV from $5.00 to $7.38 per $100 stake. Actual results can differ.
Responsible-use note
Analytics should support disciplined decision-making, not guaranteed outcomes. Bet only where legal, never risk money you cannot afford to lose, and use limits before volume increases.
FAQ
What is expected value in sports betting?
Expected value is the average profit or loss per bet when the same wager is placed at the same odds infinitely many times. Positive EV means the wager is mathematically favorable given your estimate.
How big should my EV edge be before betting?
A common floor is 2 to 3 percent EV, but the right threshold depends on market quality, estimate confidence, and bankroll. Less liquid markets typically require a larger cushion.
Why is positive EV not enough?
EV assumes your probability estimate is correct. Bad estimates, line movement after you bet, voids, and limit reductions can all turn a paper +EV play into negative realized value.
