In Productive, there is a field for just about everything, but sometimes you have your unique metric or calculation that isn't available by default.

Luckily, **you can use formulas to combine multiple fields into a custom formula field with simple mathematical operations.**

To add your formula field,** click on** **Formula** > **Add Formula**.

First, start by giving your new field a name:

Now it's time to add the values you would like to use. To select the first value, **type in the "@" symbol **- it will show a drop-down menu with a list of available values:

**Select the values** you would like to use and combine them as a formula. The following operations are supported:

**Addition ( + )****Subtraction ( - )****Multiplication ( * )****Division ( / )**

You can also put your formula in **brackets**: *( A + B) - C *

In this example, we'll create a field that will display the difference between total and remaining budget. The formula used is **Budget total** *(minus)* **Budget used.**

When finished, **click on Create Field**.

Now, the field is visible in the main view:

Formula fields are available for all **numeric** data across Productive.

## Composite Formulas

You can create a composite formula, one that is made of other formulas. For example, the field Total Time is made out of two formulas:

You can use that formula to compose other formulas as well:

## Formula Aggregations

You can set the way each formula is aggregated in the header of the data table using three different options:

- Default (preset value after the formula is created)
- Sum
- Average

To change the aggregation type, click on the formula and select **Calculation options**: