By Edge Team · · Updated
Expected value (EV) is the average result implied by a set of probabilities and payouts. It is a decision framework—not a promise that one bet, or even a large group of bets, will make money.
For a two-outcome wager:
EV = (estimated win probability × profit if won) − (estimated loss probability × stake)
Suppose a $100 bet pays $120 in profit if it wins, and you estimate a 50% chance of winning:
EV = (0.50 × $120) − (0.50 × $100) = $10
Under those assumptions, the expected value is +$10 per $100 staked. The next bet can still lose $100. The calculation is only as reliable as the 50% probability estimate and the actual payout.
For positive odds:
Probability = 100 ÷ (odds + 100)
For negative odds:
Probability = |odds| ÷ (|odds| + 100)
Examples:
These are price-implied probabilities. They are not automatically fair probabilities because a sportsbook can include margin and the estimate may differ across sources.
If your win-probability estimate is too high, a positive EV result can be an illusion. Data can be incomplete, a market can move, and two outcomes can be correlated in ways a simple calculation ignores. That is why Edge labels the number an estimate and explains how it is calculated.
The core Edge calculation converts matched prices into implied probabilities and uses their cross-book average as a market-consensus baseline. Estimated edge is that fair-value probability minus the probability implied by the offered price. Read the exact thresholds on the methodology page.
Getting +120 instead of +110 on an identical outcome is objectively a better payout. Whether either price has positive EV still depends on the outcome’s probability. Line shopping can improve the price without proving that the bet is favorable.
The free expected value calculator lets you enter American odds, your estimated win probability, and stake. It returns EV in dollars and as a percentage of stake. Try changing only the probability input to see how sensitive the result is.
EV does not tell you:
Use EV to make assumptions explicit, compare prices consistently, and audit your process. Do not use it as a guarantee.
Editorial note: Examples are hypothetical and educational. Odds and market conditions change. Review the Edge methodology, verify the final price, and never stake money you cannot afford to lose.
