Closing line value (CLV) measures whether you bet at a better price than the market's closing line. Consistently beating the close is the strongest sign your betting has a genuine, repeatable edge.
The closing line — the final price right before a game starts — is the sharpest the market ever gets, after all the money and information have gone in. If you routinely got a better number than the close, you were, on average, ahead of the market. That's skill; a single result is just variance.
You can win a bet that was a bad price, or lose a bet that was a great price — over a small sample, results tell you almost nothing. CLV tells you whether your process is beating the market now, long before the win/loss sample is big enough to be meaningful.
Compare your price to the closing price on the same side. In decimal terms, CLV% = (your odds ÷ closing odds) − 1. Positive means you beat the close.
Occasionally, through luck — but not sustainably. If your CLV is negative over a large sample, you're paying worse than the market and the edge isn't real.