> ## Documentation Index
> Fetch the complete documentation index at: https://docs.siftstack.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Step 1: Understand Calculated Channels

## Overview

**Calculated Channels** in Sift let you define custom metrics and derive new signals from existing Channels using [CEL](https://cel.dev) expressions, without modifying the original data. Sift supports two types of transformations:

* **Stateless**: Processes each data point independently, ideal for real-time computations like unit conversions or threshold checks. For example, converting a temperature Channel from Celsius to Fahrenheit.
* **Stateful**: Retains context over time, enabling trend analysis and detection of gradual changes. For example, computing a rolling average over a defined time window.