You bet an over at -110. It loses. Was it a bad bet?
Your win-loss record can't answer that, at least not quickly. Closing line value can.
The short version
The closing line is the last line and price a book offers before the game starts. By then, the market has absorbed nearly everything: injury news, lineups, weather and the money of bettors who are better informed than most.
Closing line value (CLV) is how much better your bet was than that closing number. If you bet an over at 6.5 and it closed at 7.5, you got a full point of CLV. If you bet at -110 and the same side closed at -125, you got better odds than the market's final word.
Consistently beating the close is the clearest sign a bettor has a real edge, because the closing line is the hardest number in the market to beat.
Two kinds of CLV
Line CLV. The line itself moved after you bet. You took a quarterback over 1.5 passing touchdowns and it closed at 2.5, or a pitcher under 6.5 strikeouts and it closed at 5.5. Every outcome your bet wins, the closing bet would also win, plus some it wouldn't.
Price CLV. The line stayed put but the price moved. You took over 24.5 points at -110 and it closed at -130 on the over. Same bet, but the market now charges more for it.
Line moves are easy to read. Price moves need a little math.
Calculating price CLV
Step one is turning the closing prices into a fair probability. The closing over and under together include the book's margin, so you remove it.
Say you bet an over at -110. At close, the over is -125 and the under is +105.
| Price | Implied probability |
|---|---|
| Over -125 | 125 / 225 = 55.6% |
| Under +105 | 100 / 205 = 48.8% |
| Total | 104.3% |
The 4.3% above 100% is the margin. Divide each side by the total and the fair, no-vig probability of the over at close is 55.6% / 104.3% = 53.2%. (The no-vig calculator does this step for any two-way line.)
Step two: what was your bet worth at that probability? At -110, a winning $1 bet pays about $0.909.
Expected value = 53.2% × $0.909 − 46.8% × $1 = +$0.017
That's roughly +1.7% CLV: by the market's own closing estimate, your -110 over was a +1.7% bet. It might still lose tonight. Over hundreds of bets like it, you'd expect to come out ahead.
If the over had closed at -105 instead, the same calculation comes out negative. You'd have paid more than the market ended up thinking the bet was worth.
Why CLV beats your win rate
Results are noisy. If you bet 100 props at a true 53% hit rate, your actual record will commonly land anywhere from about 48 to 58 wins. The standard deviation of a hit rate over 100 bets is about five percentage points, which is bigger than the edge you're trying to measure.
So after 100 bets, a winning record doesn't prove you're good and a losing one doesn't prove you're bad. You'd need thousands of bets for the record alone to settle it.
CLV converges much faster, because it measures each bet against the best estimate available, not against one roll of the dice. A bettor who beats the close by a couple of percent on average across a few hundred bets is very likely doing something right, whatever the scoreboard says this month.
Where CLV comes from
Betting before the news. If you bet a receiver's over before his teammate is ruled out, the line usually moves your way once the news lands.
Line shopping. Taking the best number across several books is CLV you lock in at the moment you bet. If one book is at 6.5 and the rest are at 7.5, the close usually ends up nearer the crowd than the outlier. See line shopping for player props for how much that's worth.
Spotting stale lines. A book that hasn't moved while everyone else has is offering yesterday's price. Those gaps are also where middles and arbs come from.
The caveats
CLV is an estimate, not a result. The closing line is the market's best guess, not the truth. Some closing lines are wrong too, especially on thin markets.
Props close less efficiently than spreads. A Sunday NFL spread has huge volume behind it by kickoff. A backup tight end's receptions prop has very little. CLV still tells you something on props, but treat it as stronger evidence on bigger markets.
Pick'em entries have no price. On PrizePicks or Underdog you can measure line CLV (did the line move your way?) but not price CLV.
Books notice. Consistently beating the close is exactly what sportsbooks watch for when they limit accounts.
Tracking it
To measure CLV you need three things for every bet: the line and price you took, and the line and price at close. Most bettors don't record the close, which is why they end up judging themselves on win-loss alone.
Betravon records the closing price for every graded pick and publishes the average CLV alongside wins, losses and ROI on its public track record. Whatever tool you use, the habit is the same: log the close, and judge your bets by the number you got, not just by how the game went.