I’m working with a rollup property called “Task Summary” that pulls multiple numeric values from a related database. This rollup contains several numbers that come from a formula property in my Projects database.
My goal is to create a formula that can calculate the mean value of all these numbers in the rollup. I understand that I need to find both the total sum and count of values in the collection, but I’m having trouble figuring out the right approach.
I’ve attempted using .toNumber() but this only gives me the first value from the collection. I also tried .format() without success, and I’m still getting the count instead of what I need.
The main problem is that regular rollup columns have built-in calculation options like Sum and Average at the bottom. However, when you have a rollup property that contains an array of values, these calculation options are missing entirely. That’s exactly what I’m dealing with.
Any help with the proper formula syntax would be greatly appreciated.
honestly this drove me crazy for weeks until i realized notion’s rollup calculations get weird when theres nested formulas involved. what worked for me was creating seperate rollup properties - one for sum and one for count, then divide them in a third formula property. bit messy but it works when the built-in options dissapear
The issue you’re experiencing occurs because Notion treats rollups containing formula-generated arrays differently than simple value rollups. When I faced this problem, I discovered that the calculation options disappear when the rollup contains what Notion considers “complex” data structures. Your approach with .toNumber() is correct but incomplete - it needs to be combined with proper array handling. Try using map() to process each value in the rollup array first, then apply your calculations. Create a formula like prop("Task Summary").map(current.toNumber()).sum() / prop("Task Summary").map(current.toNumber()).length() to get your average. However, this syntax might not work directly depending on your Notion version. The more reliable solution is restructuring your data flow - instead of rolling up formula results, consider rolling up the raw values and then applying your calculations in the destination database. This typically restores the missing calculation options and gives you better control over the final output.
I encountered this exact issue last month when building a project tracking system. The key insight is that when Notion can’t display the calculation options, it usually means the rollup is returning mixed data types or the source formula has inconsistent outputs. First, check your source formula in the Projects database to ensure it always returns a number, even for edge cases. Use something like if(condition, your_calculation, 0) to handle empty or invalid states. For the actual calculation, you’ll need to create two separate rollup properties: one configured to Sum and another to Count (uncheck empty). Then create a formula property that divides the sum rollup by the count rollup to get your average. This workaround has been reliable in my experience, though it requires three properties instead of one. The rollup calculation options should appear once your source data is consistently numeric.