# Math Helper

Add, divide, round and total numbers in a step.

## Do things in Math Helper

Add a **Math Helper** step and choose an **Operation**. Choose the row to see the fields of each.

- [Calculate](https://docs.gorunner.io/apps/math-helper#fields-f-calculate): Add (+) · Subtract (−) · Multiply (×) · Divide (÷) · Modulo (%) · Power (^) · Round · Round to N decimals · Floor · Ceil · Absolute · Square root · Logarithm · Minimum · Maximum · Sum (list) · Average (list) · Random in range

Later steps read a step’s output by its name: see [Use data from earlier steps](https://docs.gorunner.io/build/use-data-from-earlier-steps).

**What changed in version 2?**

New steps use version 2.0.0. A step made before keeps 1.0.0 and works as it always has. The step’s panel shows its version at the top right. On an older step it reads **v1.0.0 · 2.0.0 available**: press it to choose the version.

In 2.0.0: Results are rounded to 15 significant digits, the precision a spreadsheet uses. So `0.1 + 0.2` gives `0.3`, not `0.30000000000000004`, and **Round to N decimals** rounds `1.005` to `1.01`. Version 1.0.0 gives the raw computer answer.

## Example

Round an order’s total to cents. Add a **Math Helper** step, choose **Round to N decimals**, and set **Decimal Places** to `2`. Set **Value A** to:

```expression
{{trigger.body.total}}
```

Not in your list? See [When an app isn’t here](https://docs.gorunner.io/apps/when-an-app-isnt-here#q-not-in-list).

## For developers

In the API, which calls apps pieces, Math Helper is `pieceId: "math"` with `actionId: "calculate"`, set by `operation`. [Get an app](https://docs.gorunner.io/api/apps/get-app) returns every field.

It computes from its inputs only (`pure`). See [How versions and side effects work](https://docs.gorunner.io/apps#q-versions).

### Math Helper › Calculate

Apply a math operation to one or two numbers.

### Add (+), Subtract (−), Multiply (×), Divide (÷), Modulo (%), Power (^), Minimum and Maximum

- **Value A · Required**: The first number to work with, such as 10.
- **Value B · Required**: The second number, used with the first one, such as 3.

### Round, Floor, Ceil, Absolute and Square root

- **Value A · Required**: The first number to work with, such as 10.

### Round to N decimals

- **Value A · Required**: The first number to work with, such as 10.
- **Decimal Places · Optional**: How many digits to keep after the decimal point, such as 2 turns 3.14159 into 3.14. Default: 2.

### Logarithm

- **Value A · Required**: The first number to work with, such as 10.
- **Base · Optional**: Logarithm base (use a blank/0 for natural log e). Default: 10.

### Sum (list) and Average (list)

- **Numbers · Required**: Array of numbers, such as [1, 2, 3].

### Random in range

- **Min · Optional**: The smallest number the random result can be, such as 1. Default: 0.
- **Max · Optional**: The upper bound for the random result, such as 100. With Whole Number on it can be returned; for a decimal result the value stays just below it. Default: 100.
- **Whole Number · Optional**: Return a whole number (integer) between Min and Max, both included. Leave off for a decimal result. Off by default.

Source: https://docs.gorunner.io/apps/math-helper