# Using calculated fields

Calculated fields are updated live when a form is filled and can contain any content you’d like to. They are perfect for providing previews or to show calculated values before submission.

## Adding a calculated field

Calculated fields are just regular ACF fields. Go to your field group and add a new field of type “Calculated”. Next we need to configure what value this field should display which is done in the form settings. Head on over to your form settings and switch to the “Calculated” tab.

Under the “Calculated” tab you will find a WYSIWYG editor for each calculated field. You can add regular content and mix in field values which will be updated in real-time, similar to how field values can be included in email notifications and success messages. Mathematical arithmetic, such as addition, is not currently supported through the admin interface but can easily be achieved with a little bit of code. Read the next section for an example on how this can be done.

## Customizing calculated value

Field are not limited to static content with mixed in fields but also support using code to define more complex calculations, for example including arithmetic. Use the `af/field/calculate_value`

filter to provide your own calculation logic.

Below is an example of a calculated field which display the sum of two other fields in the form called `number_field_1`

and `number_field_2`

. Replace `FIELD_NAME`

in the example below with the name of your calculated field.