> For the complete documentation index, see [llms.txt](https://references.everstrike.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://references.everstrike.io/trading/index-price.md).

# Index Price

## Overview

The Everstrike Index Price is a derived price. It uses real-time prices from selected spot exchanges.

The Index Price supports the [Everstrike Mark Price](/trading/mark-price.md). It updates once per second.

Everstrike excludes outlier prices before calculating the average. This protects the Index Price against price manipulation.

{% hint style="info" %}
The exact outlier threshold and calculation method are not currently specified.
{% endhint %}

## Constituent exchanges

The following spot exchanges contribute prices to the Index Price:

* Kraken
* Coinbase
* Binance
* Bitfinex
* Kucoin
* Huobi
* Gate.io
* Bitget
* OKX
* Crypto.com

## Contract index prices

Everstrike calculates an Index Price for each derivatives contract.

### Perpetual options

For perpetual options, the Index Price equals the option's intrinsic value. Everstrike derives this value from its underlying perpetual futures Index Price.

When intrinsic value is zero, Everstrike uses a fallback value:

`Option Index Price = 0.05% × Underlying Futures Index Price`

For example, if the underlying futures Index Price is `$100,000`, the fallback is `$50`.