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What Is a No-Vig Price, and Why Does It Matter?

By ArchivePicks · Published

When a sportsbook posts a player prop, it does not offer both sides at a perfectly fair price. It builds in a margin, usually called the vig, juice or overround. A no-vig price is what the two sides would look like with that margin taken back out. It is one of the most useful ideas in prop research, and the arithmetic is short enough to do by hand.

This article walks through where the margin comes from, how to remove it, and what a no-vig number can and cannot tell you.

Where the vig comes from

Take a line of 64.5 receiving yards. A book might post the over at -115 and the under at -105. Those American odds convert to implied probabilities (the implied probability article shows how):

Add them: 53.49% + 51.22% = 104.71%. Two outcomes that cover every possibility (the player finishes over or under) cannot both be likely enough to total more than 100%. The extra 4.71 points is the book's margin, baked into the prices. It is how a book gets paid for running the market, whichever side wins.

A common special case is -110 on both sides. Each side implies 110 / 210 = 52.38%, and the pair totals 104.76%. That is why a bettor at -110 needs to win more than 52.38% of the time just to break even. The vig is a hurdle the price sets before any research begins.

How to remove it

The simplest method is proportional scaling. Divide each implied probability by the total so the pair sums to 100%.

Using the -115 / -105 example:

  1. Total = 53.49% + 51.22% = 104.71%.
  2. Fair over = 53.49% / 104.71% = 51.09%.
  3. Fair under = 51.22% / 104.71% = 48.92%.

The two now add up to 100%. The book's own prices, stripped of margin, say the over is very slightly more likely than the under, about 51 to 49.

You can convert back to odds if you prefer. A 51.09% chance is a ratio of 51.09 to 48.91, about 1.045. In American terms the fair over is roughly -104 and the fair under roughly +104, compared with the posted -115 and -105. The gap between posted and fair is the vig you pay on each side.

The no-vig calculator does this for any pair of American odds, and the odds converter handles the conversions in between.

A lopsided example

The method also works when the sides are uneven. Suppose a points prop is posted with the over at -150 and the under at +120.

Scaling: fair over = 60.00 / 105.45 = 56.90%, fair under = 45.45 / 105.45 = 43.10%.

Here the margin is split proportionally: the favored side gives up about 3.1 points (60.00 to 56.90) and the underdog side about 2.4 points (45.45 to 43.10). Other methods split the margin differently, for example by assuming longshots carry more of it than favorites. Proportional scaling is the easiest to follow and a fair first approximation, but it is an approximation, not a law.

What a no-vig price is used for

Seeing what the market actually thinks

The raw prices make the over look like a 53.49% proposition. The no-vig version says about 51%. When you want the market's view of a line, the second number is the honest one. If you compare a hit rate with the market, compare it with 51%, not 53.5%.

Comparing books on equal terms

Two books can post the same number with different margins. Say Book A has -115 / -105 and Book B has -110 / -110. The fair over is 51.09% at Book A and 50.00% at Book B, so Book A's market leans slightly more toward the over. The margins are 4.71% and 4.76%, nearly the same. Looking at the fair numbers first and the margin second makes the comparison cleaner than staring at the raw prices. The comparing player props across books article covers the practical side.

The base for a +EV tag

A price is "+EV against the market" when it pays more than the margin-free probability from other sources implies. That requires stripping the margin from those sources first. The full walk-through is in what +EV means in player props.

Putting a cost on the vig

Suppose the true chance of the over really is the 51.09% from above and you take it at -115. You stake 115 to win 100.

Even when the market is exactly right, the vig produces an expected loss of a few percent of the stake. That is not a flaw in the book; it is the price of the product.

Where no-vig prices fall short

The result is only as good as the market behind it. Removing the margin gives you the book's implied view, not the truth. Prop markets are thinner and less efficient than point spreads, and one book's price for a lesser player can be stale or simply wrong.

You need both sides. The method needs a price on the over and the under. Some markets show only one side, such as an alternate line or a "player to record" prop. Without the other side you cannot separate margin from probability.

It is a snapshot. Prices move with news, injuries and betting volume. A no-vig figure from this morning may not describe the line at tip-off. See line movement: what it can and cannot tell you.

It does not know about the player. A fair price is a statement about a market, not about a hamstring. It does not replace the game log, or the hit rate and its sample size.

A short checklist

  1. Convert both American prices to implied probabilities.
  2. Add them. The amount over 100% is the margin.
  3. Divide each by the total to get the no-vig chances.
  4. Compare those figures, not the raw ones, between books or against a hit rate.
  5. Treat the result as a market estimate with real uncertainty, not as a forecast.

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