Calculator

Closing Line Value Calculator (CLV)

About this calculator

By Alex Thornton · author of the MIT-licensed teachersbettextbook library · Last reviewed 24 July 2026

Did you actually beat the close? This de-vigs the closing price, subtracts what yours implied, and grades what is left.

Want every bet graded automatically, with the CLV lesson on each one? Open the tool in the app →

A closing line value calculator compares the price you took with the market’s final, de-vigged price. Positive means you beat the close: you got a better number than the market’s last word.

Why the close and not the result

One bet tells you nothing. A 55% shot loses nearly half the time, and a terrible bet wins plenty of Sundays. Results need hundreds of settled bets before they say anything at all.

The closing line gets there faster. It is the market's best guess after every injury report, every line move and all the money is in. If you kept getting a better number than the close, you were early on something real.

So this compares your price against the de-vigged fair probability at close, in probability points. Positive means you bought cheaper than the market ended up.

The letter grade is a scale, not a verdict. Anything that beat the close is at least a B, and A+ is reserved for betting nothing at all.

Want more math?the Nerd Corner

\text{CLV} = p_{\text{close}} - q_{\text{you}}, \qquad p_{\text{close}} = \dfrac{q_i}{q_A + q_B}, \qquad q_{\text{you}} = \dfrac{100}{\text{price}+100}

where:

$q_A,\ q_B$ : the vig-inclusive implied probabilities of the two closing prices. They sum to more than 1.
$p_{\text{close}}$ : the de-vigged fair closing probability of the side you bet (proportional shown; power and Shin are options in the form).
$q_{\text{you}}$ : the probability your price implied, from the same American-odds conversion. Use $-m/(100-m)$ for a negative price.
$\text{CLV}$ : the difference, in probability points. Anything above zero beat the close; +1.0 points or better grades an A.

Worked example: the numbers in the form below

You took side B at +130; the market closed −140 / +120:

+130 \Rightarrow q_{\text{you}} = \tfrac{100}{230} = 43.48\%

-140 \Rightarrow q_A = 58.33\%, \quad +120 \Rightarrow q_B = 45.45\% \quad (\text{sum } 103.79\%)

p_{\text{close}} = \dfrac{0.4545}{1.0379} = 43.80\% \qquad \Rightarrow \qquad \text{CLV} = 43.80\% - 43.48\% = +0.32\ \text{pts}

Three tenths of a point on the right side of the close: a B, because it beat the close. Same market, same side: +134 would have graded an A, and +115 an F.

How the closing line value calculation works

Three steps, all of them in the formula above: convert your price to the probability it implies, de-vig the two closing prices for the fair closing probability of your side, then subtract. Positive CLV means the fair close sat above the price you paid: you bought the side cheaper than the market’s final number. Negative means the market moved past you.

Step two is not optional. Compare against the raw closing price and you are measuring against a number inflated by the closing book’s margin: on the 3.79% hold above, that error is worth roughly 1.7 points on this side alone, five times the CLV actually measured.

The A–F grade scale

Raw probability points are hard to feel, so the calculator grades them.

A: +1.0 points or more. You beat the close by a clear margin.
B: 0.0 to +1.0 points. You beat the close.
C: 0.0 down to −1.0 points. The close moved past you, barely.
D: −1.0 to −2.5 points.
F: below −2.5 points, well on the wrong side.

Zero is the line that carries the meaning, so zero is where B starts: a price that beat the close cannot grade below a B, however narrowly it beat it.

Against the same −140 / +120 close, the whole A-to-F range spans about 18 cents of American price, from +134 down to +116: roughly four and a half cents per grade. That is why a grade is a band and not a decimal.

When to use this calculator

After the close, on a bet already placed. CLV is a post-mortem on the price, not a signal about the game.
To test an edge in dozens of bets instead of hundreds. Win rate is buried in variance; average CLV converges far faster.
To compare two sources of numbers. The one with the higher average CLV is buying better prices, whatever the win-loss records say.

Common mistakes

Comparing to the raw closing price. The close carries vig too; skipping the de-vig inflates every grade by roughly half the closing hold.
Mixing de-vig methods between bets. One method, held fixed across the whole sample, or the average means nothing.
Grading a single bet. One CLV number is noise. The statistic is the season average, which is why the Report Card GPA is the plain mean of grade points.
Grading a market that re-priced for a non-informational reason. A postponement, a late scratch or a re-hung line moves the close for reasons unrelated to your read. Those bets belong out of the sample.

Check this number yourself

Same math as the MIT-licensed teachersbettextbook package, two public functions and a subtraction: devig() on the closing pair, moneyline_to_prob() on your price.

pip install teachersbettextbook

>>> from teachersbettextbook import devig, moneyline_to_prob
>>> p_close = devig(-140, 120, method='proportional')[1]
>>> p_close - moneyline_to_prob(130)
0.003173595683909902

Same inputs, same digits, no account required. More in open source.

The de-vig step behind every grade has its own tool, the no-vig calculator. Size a graded price with the Kelly calculator, check a single bet with the expected value calculator, and read the full method in closing line value explained.

Frequently asked questions

Why is closing line value the best measure of betting skill?

The closing line is the market’s sharpest estimate, set after all money and information have arrived. Beating it consistently means you bought better than the final consensus. Average CLV converges on your true edge within dozens of bets; win rate stays buried in variance for hundreds.

Does closing line value depend on which de-vig method you use?

On a thin result, yes: enough to flip the sign. A +130 price against a −140/+120 close grades +0.32 points under proportional de-vigging, −0.03 under power and +0.08 under Shin. All three land in the same C band, which is why grades are bands and not decimals. A CLV smaller than the spread between methods is not evidence of anything.

Is positive closing line value the same as profit?

No. CLV measures the quality of the price you bought, not the result of the bet. A bet can beat the close by four points and lose, or lose to the close and win. Separating the decision from the outcome is exactly why CLV converges faster.