---
title: "Computed measurements explained"
slug: "computed-measurements-explained"
updated: 2025-08-12T13:18:58Z
published: 2025-08-18T11:50:28Z
canonical: "docs.calculus.group/computed-measurements-explained"
---

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

# Computed measurements explained

## Introduction

A computed measurement allows the user to perform mathematical operations on measurements, and then display the result in a widget.

---

## Instructions

A computed measure uses square brackets to use a measurement path as a parameter, and always has the following format:

```vim
[gateway|sensor]
[gateway|slave|sensor]
```

Optionally, you can specify a slave and aggregation:

```vim
[gateway|sensor#AVG]
[gateway|slave|sensor#MAX]
```

You can find more information about aggregation in the article [Aggregate functions explained](/v1/docs/en/aggregate-functions-explained).

You can then use these parameters to perform mathematical calculations. For example, if you want to multiply an Open Weather humidity reading by 1000:

```vim
[openweather|humidity] * 1000
```

It is also possible to use two or more sensors:

```vim
[openweather|humidity] + [openweather|clouds]
[openweather|humidity] + [openweather|clouds] * 2
```

For the evaluation of mathematical expressions, we use NCalc. The possibilities with computed measurements are further explained in these articles:

[NCalc functies](https://github.com/ncalc/ncalc/wiki/Functions) [NCalc operators](https://github.com/ncalc/ncalc/wiki/Operators)

## Setting up a computed measurement

When adding a new widget, you first choose a data source and a sensor. By doing so, you have already chosen a gateway (with optional slave) and a sensor for your measurement path. This way, your computed measurement will already have filled in the measurement path for you, including the square brackets. If needed, you can add an aggregation type and mathematical operators.