Closing Line Value Explained
Closing line value compares the price a bettor took with the final price before the game. See how to calculate it, why analysts treat it as a measure of skill rather than luck, and where it misleads.
Closing line value, usually shortened to CLV, is a way of asking whether the price you got on a baseball bet was better or worse than the price the market settled on just before the first pitch. It does not tell you whether the bet won. It tells you whether the bet was priced well, which is a different thing and, for people who analyze betting markets, a more useful one. A bet can win at a poor price and lose at a good one, and over a small number of bets the results are mostly noise.
This article explains what the closing line is, how to calculate CLV with real arithmetic, why the number has the status it has among people who study betting markets, and what it cannot do. It is an explanation of a concept, not advice to bet. Sports betting carries a risk of loss, is for adults of legal age where it is legal, and offers no guarantee of profit. If gambling is causing you or someone you know problems, the US helpline is 1-800-GAMBLER.
What the closing line is
A sportsbook posts a price for each side of a game, such as a moneyline, a run line or a total, and changes it as bettors place wagers and as new information arrives. The closing line is the last price available before the game starts, which in baseball means before the first pitch. After that, the game moves to live betting, where prices change pitch by pitch, a subject covered in live betting on baseball.
The closing line differs from the opening line, which is the first number posted, usually many hours or a day earlier. Between the two, the market has absorbed a lot: the confirmation of the starting pitchers, the posting of lineups, weather forecasts, injury news and the wagers of every kind of bettor. How sportsbooks set baseball lines describes the starting point; the closing line is where the process ends.
Reading American odds as probabilities
CLV depends on converting prices into probabilities. A price in American format implies a chance that the outcome occurs, before the sportsbook's margin. For a negative price, the implied probability is the price's absolute value divided by that value plus 100. For a positive price, it is 100 divided by the price plus 100.
| American odds | Implied probability |
|---|---|
| -200 | 66.7% |
| -150 | 60.0% |
| -120 | 54.5% |
| -110 | 52.4% |
| +100 | 50.0% |
| +110 | 47.6% |
| +150 | 40.0% |
| +200 | 33.3% |
A two-sided market where both sides cost -110 implies 52.4 percent for each side, and the two figures add to 104.8 percent. The extra 4.8 points are the sportsbook's margin, called the vig or the overround. This matters because the closing price of a single side includes the margin, and a fair comparison has to take it out.
A worked example
Suppose you take Team A at +120. Later, as the game approaches, the market moves toward Team A, and the closing prices are Team A at +105 and Team B at -125.
First, the implied probabilities at the close. Team A at +105 is 100 divided by 205, or 48.78 percent. Team B at -125 is 125 divided by 225, or 55.56 percent. Those add to 104.34 percent, so the margin is 4.34 points. To remove it, divide each by 1.0434. Team A's fair closing probability is 46.75 percent and Team B's is 53.25 percent.
Second, your price. At +120 your implied probability was 45.45 percent, which is lower than the fair closing figure of 46.75 percent. You paid less for the outcome than the closing market says it was worth, and that gap is positive CLV.
Third, put a number on it. If the closing line is a fair estimate of the true probability, the expected value of your bet per unit staked is the probability of winning times the profit, minus the probability of losing times the stake: 0.4675 times 1.20, minus 0.5325, which equals about +0.029. In other words, if the close is right, the bet was worth about 2.9 percent of the stake. The comparison of raw prices gives a different and larger number, since +120 pays 2.20 per unit staked and +105 pays 2.05: dividing and subtracting one gives 7.3 percent. The 7.3 percent figure overstates the edge, because the closing price includes the sportsbook's margin, while the 2.9 percent figure removes it.
The same arithmetic runs in the other direction. If you had taken Team A at +105 and the market closed at +120, your implied probability of 48.78 percent would have been higher than the closing figure of 45.45 percent. That is negative CLV: you paid more than the market later said the outcome was worth.
Why the close is treated as the best estimate
The reasoning is simple. The closing line contains all of the information the market has gathered, from the sharpest bettors and the sportsbook's own adjustments to the final weather and lineup news. In most major markets it is regarded as the most accurate public estimate of the true probability, though not a perfect one. A bettor who consistently gets better prices than the close is, on average, buying outcomes for less than the best available estimate of their worth, and that is evidence of skill.
This is more persuasive than win-loss results because baseball is noisy. Even a strong favorite loses often, and the margin between a good bet and a break-even bet is small. Consider a bettor with a true 2 percent edge on bets near even money. The expected profit is 0.02 units per bet, while the standard deviation of one bet is about 1 unit. Over 100 bets the expected profit is 2 units against a standard deviation of 10, so the result is dominated by luck. The expected profit only equals one standard deviation after about 2,500 bets, because 0.02 times the square root of n equals 1 when n is 2,500. A record of wins and losses takes years to read, while the closing price can be compared the moment the game starts.
Moves that carry CLV in baseball
Baseball lines move for specific reasons, and understanding them explains much of the CLV that people measure.
- Starting pitcher changes. If a listed pitcher is replaced, the line can move a lot. Listed pitchers versus action explains how bets are handled when a pitcher changes, and the close reflects the final pitcher.
- Lineups. Lineup cards are usually posted a few hours before the game, and a missing star hitter moves the price.
- Weather and wind. Totals respond to forecasts, as described in weather, wind and baseball totals.
- Public and sharp money. Heavy wagering on one side moves the price toward the other, and sportsbooks move lines in response to the wagers of bettors they respect.
For first-five-inning bets, the same logic applies to a narrower market that depends mainly on the starters; see first-five-innings bets. A bettor who tracked only one of these markets would have a different CLV profile from one who tracked all of them.
Totals, run lines and the half run
CLV applies to every kind of price, and it comes in two forms. For a moneyline the difference is in the price, as in the worked example. For a total or a run line the number itself can move. If you take the Over on 8 at -110 and the total closes at 8.5, you got a better number, because a game that lands on exactly 8 is a push on your bet but a loss on the closing number. How much the extra half run is worth depends on how often games finish at that total, which is why analysts do not treat every half run as equal. The pricing of those markets is covered in moneyline, run line and totals explained.
How to track it
A simple record needs four items for each bet: the price and number you took, the sportsbook, the time, and the closing price at the same sportsbook. Convert both prices to implied probabilities, remove the margin from the close if you want an expected-value estimate, and subtract. The average over many bets is your CLV. It has to be a like-for-like comparison, the same book and the same market, or the number means little.
Three practical notes follow. Record the closing price at the book where you bet, since books differ. Keep the sample large before you draw conclusions, because CLV is itself an average of noisy differences. And report the figure the way you calculated it, because a CLV based on raw prices will always look larger than one with the margin removed.
CLV and results are different questions
It helps to separate three numbers that people often blur together. The first is return on investment, which is profit divided by the amount wagered and depends entirely on results. The second is the win rate, which is the share of bets that won and says nothing about price, since a heavy favorite wins most of the time and still can be a poor bet. The third is CLV, which is about price alone.
A short illustration shows the gap. Imagine a bettor who places 200 wagers on underdogs at plus-money prices that, on average, close 2 percent better than the market's fair number. Over those 200 bets the expected return is positive but small, about 4 units on 200 staked. The standard deviation is roughly 15 units, since each bet carries a little more than 1 unit of spread and the square root of 200 is about 14. So the bettor ending the stretch down 10 units would be less than one standard deviation from the expectation, and nothing about that result would show whether the prices were good. The closing prices, by contrast, are already known, and they show that every bet was placed at a price better than the market's final number.
None of this makes results irrelevant. Over a long enough record, a bettor with persistently positive CLV and persistently negative results should suspect something is wrong with the measurement: a poor reference book, a margin that was not removed or a market too thin to trust.
An illustrative day of line movement
Because real lines change quickly, a hypothetical sequence is the easiest way to see how CLV accumulates. Suppose a game opens with the home team at -135 and the visitors at +115. In the morning the lines drift to -140 and +120 after wagering on the home team. Mid-afternoon, news arrives that the visiting team's starter has been scratched and a different pitcher replaces him, and the line moves to -165 and +140. Lineups post, the weather is clear, and the game closes at -160 and +135.
A bettor who took the home team at -135 in the morning and held that price through the close at -160 has positive CLV, because the price the bettor got is cheaper than the closing price. A bettor who took the visitors at +115 at the open and then saw them close at +135 has negative CLV, because the payout that was available later was bigger. The first bettor was right about the direction of the move, and nothing about this example says either bet won. The point is only that the closing price is the fixed reference against which both are measured.
Where the closing line is weaker
The closing line is only as good as the market behind it. Large markets such as major-league moneylines attract many informed bettors, and the closing price tends to be efficient. Thinner markets have fewer informed participants and lower limits, and their closing prices can be less reliable. That includes player props, alternate lines and games in smaller leagues. The Korean Baseball Organization, for instance, has a smaller betting market than Major League Baseball, so a closing line there carries less information than an MLB one.
The same caution applies to the line you are measuring against. A sportsbook that is slow to update will have a closing price that lags the market, and a bettor who compares against a stale close will overstate the result. Some analysts compare against a reference book or an average of several books to guard against this.
Common mistakes
- Judging by results. A short run of winning bets with poor prices is luck, and a short run of losing bets with good prices is also luck.
- Mixing prices. Comparing your price at one book to a close at another produces a number that reflects the difference between books.
- Ignoring the margin. Treating the closing price as a fair probability exaggerates CLV.
- Treating CLV as a guarantee. Positive CLV is evidence of a good price, not a promise of profit. Variance, limits on accounts and the margin all stand between a good price and money. Some sportsbooks limit customers who regularly beat the close, according to widely reported accounts.
- Chasing the number. Waiting for a price to move can leave you with no bet at all, or with a worse one.
Common questions
Does positive CLV mean a bet will win? No. It means the price was better than the final market price. The bet can still lose, since even a favorable price is a probability.
Can a bettor lose money with positive CLV? Yes, over a small sample. The expected result is positive if the close is accurate, but luck dominates short runs.
Is the closing line the true probability? It is the market's best public estimate, not a certainty. Where the market is thin, the estimate is rougher.
Is CLV only for professionals? No, anyone can calculate it, but it is a tool for analysis and not a strategy for making money.
Where can I get help with gambling problems? Call 1-800-GAMBLER in the United States, or visit the National Council on Problem Gambling.
Where to go next
If you want to see the prices that go into this, the odds page shows current lines, and the baseball betting topic page collects the site's coverage. Treat any of this as information about how markets work, and never bet more than you can afford to lose.