# No-vig calculator: remove the vig, get fair odds

> Independent. Not affiliated with, endorsed by or sponsored by Novig.

Canonical: https://novigapi.com/no-vig-calculator
Method checked: 2026-11-12
Interactive tool: https://novigapi.com/no-vig-calculator (prefill with ?a=&b=)

A no-vig calculator removes the bookmaker's margin from a set of prices to estimate fair odds. At -110 / -110 the book sums to 104.76%, so each side is fair at 50.00% (+100). Novig is an exchange that quotes percentages, so its two-sided mid is already close to no-vig (Novig docs, checked 12 Nov 2026).

## Worked example

Worked example: fair price by method

| Market, method | Fair A | A American | Fair B | B American |
| --- | --- | --- | --- | --- |
| -110 / -110, multiplicative | 50.00% | -100 | 50.00% | -100 |
| -300 / +240, multiplicative | 71.83% | -255 | 28.17% | +255 |
| -300 / +240, additive | 72.79% | -268 | 27.21% | +268 |
| -300 / +240, power | 73.31% | -275 | 26.69% | +275 |
| -300 / +240, shin | 72.79% | -268 | 27.21% | +268 |

## How the four devig methods work

Every method starts from implied probabilities: for American odds below zero, p = -odds / (-odds + 100); above zero, p = 100 / (odds + 100). The implied probabilities of all outcomes add up to more than 100%, and that excess is the overround. Each method decides how to take the excess back out.

```
multiplicative: p_i = q_i / sum(q)
additive:       p_i = q_i - (sum(q) - 1) / n
power:          p_i = q_i ^ k, with k chosen so sum(p) = 1
Shin:           p_i = (sqrt(z^2 + 4(1 - z) q_i^2 / S) - z) / (2(1 - z))
```

- **Multiplicative** spreads the margin in proportion to each price. It is the default and the right choice for even markets.
- **Additive** takes the same number of points off every outcome. It can push a big longshot below zero, so the tool falls back to multiplicative when that happens.
- **Power** raises each implied probability to the same exponent. It takes more margin off longshots, which matches how books shade favourite-longshot markets.
- **Shin** models a share z of informed money and solves for it. It is the standard method in academic work on longshot bias.

## Why Novig prices are close to no-vig already

Novig is a peer-to-peer exchange: the book holds bids only, so the price to buy one side is 1 minus the best bid on the other side. The fair price of a two-outcome market is the mid of the bid and that implied ask. The only gap is the bid-ask spread, and on liquid markets it is one or two points. Pregame fills on game markets carry no fee; live fills pay a taker fee of 0.06 x P x (1 - P) per $1 of payout.

```
fair_yes = (bid_yes + (1 - bid_no)) / 2
```
The fair price this site computes for every two-sided Novig market.

## How to use it

1. Enter the price of each outcome in any format: American, decimal, percent or fractional.
2. Pick a devig method, or compare all four in the method table.
3. Read the fair probability and fair American odds for each outcome, plus the overround and hold.

## Questions

### What is a no-vig calculator?

It strips the bookmaker's margin from a market so the implied probabilities add up to exactly 100%, giving the fair odds of each side.

### Which devig method is most accurate?

For two even sides all four agree. For lopsided markets, power and Shin usually beat multiplicative because books shade longshots more than favourites.

### Is Novig no-vig?

Novig is an exchange, so it adds no vig of its own. The two-sided mid of its book is the fair price; live takers pay a small fee of 0.06 x P x (1 - P) per $1 of payout.

### Can I use a Novig percentage here?

Yes. Type 54% or 0.54 and the tool reads it as a probability.

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