How to Use Sum Values in Notion Database Calculations?

Reader's Question

Is there a way to calculate the formula field on the right (usage frequency proportion) based on the data on the left?

For example: for the row with 6, the formula field (usage frequency proportion) = 6/15

My Answer

Notion currently doesn't support directly using Sum values in Formula calculations. You can only achieve this indirectly.

This involves several Notion features, including:

1. Relation and basic usage of Rollup
2. Using the map function
3. Using the format() function to convert numbers into text that can be concatenated

The general principle and process are as follows:

1. Create a database called "Count Total"
2. In the "Frequency Statistics" database, create a template. The template's purpose is to automatically create a Relation to the "Count Total" statistics page whenever a new page is created
3. In the "Count Total" database, use a Rollup field to calculate the sum of all related pages' numbers
4. In the "Frequency Statistics" database, use the map function to retrieve the Rollup value from "Count Total", which can then be used in calculations

The specific formula is as follows:

prop("Number").format()+"/"+prop("Count Total").map(current.prop("Summary")).format()

Final result:

If you're not yet familiar with Formula 2.0's new features, you can first read a deep dive into Notion Formula 2.0 to learn about the map function and more.

Latest update: If your goal is only to display Rollup summary results as dollars, euros, percentages, or similar formats, you can now use Rollup number formatting directly instead of adding formulas just for display formatting.

Method 2: Skip the Rollup field and use the map function directly

prop("Number").format()+"/"+prop("Count Total").map(current.prop("Frequency Statistics").map(current.prop("Number")).sum()).format()