What is expected value?
A plain-English guide to EV — what expected value means, how to calculate it from probability and price, and why it, not any single result, decides whether a bet was smart.
Expected value (EV) is the average profit or loss a bet would return if you could place it over and over forever. You compute it by multiplying each outcome by its true probability, adding the results, and subtracting the stake. A positive-EV bet makes money long-run; a negative-EV bet bleeds it. Every disciplined bettor tries to keep EV positive, which requires estimating real probabilities more accurately than the price implies.
A single bet can win or lose regardless of whether it was smart. EV separates the decision from the result: a +EV bet can lose tonight and still be correct, and a −EV bet can win and still be a mistake. Judging bets by EV instead of by outcome is what turns gambling into a repeatable process.
EV = (probability of winning × profit if you win) − (probability of losing × stake). At −110 odds you risk $110 to win $100. If your model says you win 55% of the time, EV = (0.55 × $100) − (0.45 × $110) = $55 − $49.50 = +$5.50 per $110 risked — positive, but only if that 55% estimate is actually right.
That last clause is the whole game. EV is only as good as your probability estimate, and the market's price already encodes a very sharp estimate. Our own ledger shows why humility matters here: a 56.5% win rate looks like clear +EV, yet our closing-line value runs roughly flat (+0.39pp), meaning the market was pricing those same games about as well as we were.
What is expected value in sports betting?Expected value is the average profit or loss a bet returns if repeated many times, found by weighting each outcome's payoff by its true probability and subtracting the stake. Positive EV means the bet makes money long-run; negative EV means it loses.
Can a bet be +EV and still lose?Yes. EV describes the long-run average, not any single result. A positive-EV bet can lose tonight and a negative-EV bet can win — which is exactly why disciplined bettors judge decisions by EV rather than by outcome.
How is EV related to CLV?Closing line value is the market's verdict on whether your bet was +EV. If you consistently beat the closing line, you were finding positive expected value the market later confirmed. Signal Labs' CLV runs roughly flat, so we do not claim a proven long-run EV edge.