Expected Value (EV) in Betting

Expected value (EV) is the average amount you'd win or lose on a bet if you could make it thousands of times. A bet with positive EV (+EV) makes money over the long run; a −EV bet loses. Finding +EV bets is the entire game.

The idea in one sentence

A bet is +EV when the price you get pays more than the true probability of winning justifies - in other words, when the odds are better than fair.

The formula

EV = (probability of winning × profit if you win) − (probability of losing × stake). If that number is positive, the bet is +EV.

Worked example

You bet $100 on a team at +120 (decimal 2.20). A sharp, no-vig line says their true probability of winning is 50%.

• Win 50% of the time → profit $120.
• Lose 50% of the time → lose $100.
• EV = (0.50 × $120) − (0.50 × $100) = $60 − $50 = +$10 per $100 bet.

That's a +10% EV bet. You won't win every time - you'll lose about half - but repeated many times, you net $10 for every $100 risked. That's how professionals think: not "will this bet win?" but "is this price better than fair?"

Where the true probability comes from

You can't compute EV without an estimate of the real probability. The best free estimate is the no-vig fair line from a tight market—remove the vig using our No-Vig Fair Odds Calculator and you get a true probability benchmark far more accurate than any hunch.

EV vs win rate

A common beginner trap is chasing high win rates. You can win 70% of your bets and still lose money if you're always laying huge juice on favorites. Conversely, a bettor hitting 45% on underdogs at great prices can crush it. EV, not win rate, determines profit.