# Vig

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Canonical: https://novigapi.com/learn/vig

The vig is the margin a sportsbook builds into its odds, so that the implied probabilities of all outcomes add up to more than 100%.

```
vig = 1 - 1 / (q_1 + q_2 + ... + q_n), where q_i is the implied probability of outcome i
```

The vig, short for vigorish and also called juice, is the price a sportsbook charges for taking your bet. It is not listed as a separate fee. Instead the book shades every price slightly against you, so the odds on all sides of a market imply more than a 100% chance in total. The extra above 100% is the book's built-in edge, and the vig is the share of every dollar wagered the book expects to keep if it takes balanced action.

## How it works

Convert each price to an implied probability, add them up, and compare the sum to 1. A fair coin flip priced fairly would be +100 on both sides, implying 50% and 50%. A standard sportsbook prices it at -110 on both sides instead. Each -110 implies 110 / 210 = 52.381%, so the two sides sum to 104.762%. If the book takes $110 on each side it collects $220, pays the winner $210 and keeps $10. That $10 on $220 of handle is the vig: 4.545%.

```
q = |A| / (|A| + 100) for negative American odds A; q = 100 / (A + 100) for positive A
```
Sum q across every outcome. The excess over 1 is the overround; 1 - 1/sum is the vig as a share of handle.

## Worked example

Vig on two common two-way markets

| Market | Side A | Side B | Implied A | Implied B | Sum | Vig |
| --- | --- | --- | --- | --- | --- | --- |
| Spread | -110 | -110 | 52.381% | 52.381% | 104.762% | 4.545% |
| Moneyline | -150 | +130 | 60.000% | 43.478% | 103.478% | 3.361% |


The moneyline in the second row carries less vig than the standard spread even though the prices look lopsided. Comparing vig across books and markets is easiest with the [hold calculator](https://novigapi.com/hold-calculator), and stripping it out to find the fair price is what the [no-vig calculator](https://novigapi.com/no-vig-calculator) does.

## On Novig

Novig is an exchange, so there is no house shading both sides. Prices are shown as percentages, which are probabilities, and the book holds bids only: the ask on one outcome is 1 minus the best bid on the other outcome. The cost of trading is the gap between bid and ask plus an explicit taker fee of 0.06 x P x (1 - P) per $1 of payout. Per [Novig trading fees](https://docs.novig.com/api/concepts/fees) (checked 12 Nov 2026), that fee applies on game markets only while the event is live, so a pregame fill on a game line carries no fee at all.

## Common mistakes

- Reading -110 as a 10% fee. The vig on a -110/-110 market is 4.545% of handle, not 10%.
- Treating the vig as split evenly between sides. Books often load more of it onto the popular side or onto long shots.
- Comparing raw prices across books without removing the vig first. Two books can show the same favorite price with very different margins.

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