# How Bueno Calculates Rarity

Bueno uses two popular methods for calculating the rarity of an NFT, **Rarity Score** and **Average Trait Rarity**. Understanding these methods will help you determine  the uniqueness of each NFT in your collection.

## Rarity Score

**Rarity scoring** is a straightforward and dependable method for assessing the rarity of an NFT. The rarity score for a token is the sum of trait scores:

**`Trait Rarity Score`**` ``= 1 / ([Number of Items with that Trait Value] / [Total Number of Items in Collection])`

This simple calculation gives consistent results for many NFT collection and serves as the basis for rarity rankings on several NFT platforms, including popular marketplaces.

## Average Trait Rarity

**Average trait rarity** is another way to calculate NFT rarity. This method is better suited for collections that have tokens containing a varying numbers of total traits. It works by **averaging the rarity score of its individual traits.**

For example, if an NFT possesses 2 traits:

* Trait A = 50%
* Trait B  = 10%

The average trait rarity would be: `(50+10) / 2 = 30%`

However, a common drawback with this approach is that it places considerable emphasis on the *combined* rarity of all traits, potentially undervaluing an exceptionally rare *single* trait, and causing the overall rarity value to be diluted by less rare traits. 

## Rarity Rank

The Rarity Rank for a token is simply how unique that NFT is relative to the collection. A rarity rank of 1 means that NFT is the most rare.

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When determining the **rarity rank** of a token, the **rarity score** is used.
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