What is Expected Value?
Expected value (EV) is the average profit or loss a bet pays per dollar staked if you repeated it under the same odds and probability forever.
Also known as: EV, +EV, -EV
Every bet has a true win probability and a price (odds). Expected value compares the two: if your win probability is higher than the implied probability of the odds, the bet is +EV and pays you over the long run; if lower, it is −EV and the book is paying itself. EV is the single most important number a serious bettor tracks, because it cuts through the noise of any single result.
Example
You give the Lakers a 55% chance to cover. The book is offering +110 (decimal 2.10), which implies 47.6%. EV per $1 = 0.55 × 1.10 − 0.45 = +0.155 — a 15.5% edge.
Related terms
The probability of a result that a sportsbook's odds are pricing in — calculated as one divided by the decimal odds.
The bet-sizing formula that maximises long-run bankroll growth, given an edge and a price.
The percentage-point gap between your win probability and the book's implied probability — your projected long-run advantage.
Betting only when your estimated win probability is higher than the bookmaker's implied probability.
See expected value applied to a real slate
NotaSportsGuru runs the math behind every published leg — Parlay of the Day, player props, match lines — with the model’s expected value and edge on every line.