# Summarize linked values with a rollup

- Product: Clastly
- Category: Fields
- Type: How-to
- Updated: 2026-10-29
- URL: https://www.clastly.com/support/fields/rollup/

Use a rollup to display values from linked records or summarize them with calculations such as a sum or average.

## Add a rollup field

Rollups use values from records linked through a relation. Create a relation field in the collection where you want the rollup, then link the records you want to summarize. If you haven't created a relation, follow [Link records with a relation](https://www.clastly.com/support/fields/relation.md) first. To total amounts, add a number field in the linked collection and enter the amounts.

1. Touch and hold the collection where you want the rollup in the collection list and open :ui[Edit Collection].
2. Tap :ui[Add Field].
3. Choose :ui[Rollup] under :ui[Field Type] and enter a :ui[Field Name].
4. Under :ui[Relation], choose the relation to use.
5. Under :ui[Target Field], choose the field to summarize from the linked records.
6. Choose a summary method under :ui[Calculation]. To add amounts, choose :ui[Sum].
7. Tap :ui[Done]. The rollup result appears in the record's details.


Changes to linked values are reflected in the summary. You can't enter a rollup result directly.

## Choose a summary method

Available calculations depend on the target field's type. For numbers, you can choose a sum or average; for dates, the earliest or latest date; and for checkboxes, the number of checked values. You can also display a list of linked values. If Sum isn't available, make sure the target field is a number field.

If you purchased Clastly Pro but can't set up the field, see [Clastly Pro features aren't available after purchase](https://www.clastly.com/support/pro/pro-not-unlocked.md).