Expected Value (EV) in Sports Betting

Expected value is the average result of a bet per unit staked if the same bet could be repeated many times. The formula: EV = (win probability x profit if you win) - (loss probability x amount staked).

A positive number means the bet makes money on average over the long run; a negative number means it loses on average. Almost every bet at a sportsbook's posted price is slightly negative EV for the bettor, because the price includes the book's margin.

Take a prop at +100 odds, meaning a $100 bet wins $100 in profit. Suppose your research says the player clears the line 55 percent of the time.

EV = (0.55 x $100) - (0.45 x $100) = $55 - $45 = +$10. On average this bet earns $10 per $100 staked, a 10 percent edge. Any single bet still loses 45 percent of the time; the edge only shows up across many bets.

Every price implies a probability. Odds of +100 imply 50 percent, because risking 100 to win 100 breaks even only at a 50 percent win rate. For negative American odds, implied probability equals risk divided by (risk plus win): odds of -110 imply 110 / 210, about 52.4 percent.

Positive EV exists exactly when your estimated probability beats the implied probability. In the example above, 55 percent against an implied 50 percent is the entire edge.

Add up the implied probabilities on both sides of a market and the total exceeds 100 percent. A standard -110 / -110 prop implies about 52.4 percent on each side, 104.8 percent in total; the extra 4.8 percent is the book's margin, often called the vig.

The margin is the hurdle every bet must clear. Your estimate does not just need to beat a coin flip; it needs to beat an implied probability that already includes the book's cut.

EV tools automate the comparison. They estimate a fair probability for each outcome, usually from statistical projections or from sharper reference prices, convert the book's odds into an implied probability, and flag markets where the gap is positive.

IntelliPickz, for example, calculates EV by comparing sportsbook lines against statistical projections built from historical performance data, refreshed alongside odds every 15 minutes. Other tools use sharp-book consensus prices instead of projections. Either approach lives or dies on the quality of its probability estimate.

EV is a long-run average, not a prediction. A 10 percent edge still loses nearly half of its individual bets, and losing streaks long enough to feel wrong are statistically normal. This is variance, and it is why bankroll management matters as much as bet selection.

The bigger risk is estimate error: an EV figure is only as good as the win probability behind it. Treat any single number skeptically, prefer small consistent stakes, and remember that books may limit accounts that consistently beat their prices.