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A Relation links database pages. A Rollup displays or calculates values from those linked pages. Use a relation when you need to say which project belongs to which client. Add a rollup when the client page also needs information from its projects, such as their total planned budget or earliest deadline.
You can use a relation on its own. A rollup needs a relation to read through: it does not choose the linked records for you. Notion’s rollup instructions start with an existing relation, then ask which property to read and which calculation to apply.
Choose by the question you need to answer
| Your question | Property to use | What it supplies |
|---|---|---|
| Which client owns this project? | Relation in Projects, pointing to Clients | A selected client page you can open. |
| Which projects are linked to this client? | Relation in Clients, pointing to Projects | The linked project pages. |
| Which distinct statuses do those projects have? | Rollup using Projects → Status → Show unique values | The different status values on the linked projects. |
| What is their total planned budget? | Rollup using Projects → Planned budget → Sum | A total of the linked projects’ numeric budget values. |
A rollup is useful for displaying values as well as doing arithmetic. Show unique values returns distinct values from the selected property; Sum answers a numeric question. Pick the question first, then the calculation.
I would keep the relation alone if the client page only needs a list of projects. Adding a rollup that repeats the same information makes the page harder to read without giving you another answer.
For a nonnumeric example, suppose both linked projects have an example Status value of In progress. A Status rollup using Show unique values supplies that value once; it does not add the project budgets or tell you which project to open. The relation still supplies the linked pages. Add a separate rollup only when its answer helps the reader of the client page.
You may not need a rollup merely to show a detail beside each linked page. Notion lets you display selected properties inside the relation field: open a database page, click the relation field, choose •••, and move the desired property into Shown in relation. Showing each project's Owner there is a different job from calculating one total across those projects.
One client, two linked projects
Consider an example client, North Studio, linked to Brand refresh and Website launch. Their Planned budget Number properties contain 3,200 and 4,800, both in USD. A Total planned budget rollup on North Studio has three inputs:
- Relation: Projects, containing those two project pages.
- Property: Planned budget, on the linked projects.
- Calculation: Sum.
Here is the source data to inspect. Discovery is in the same Projects database, but is not selected in North Studio's Projects relation.
| Project | Planned budget (USD) | Linked to North Studio? |
|---|---|---|
| Brand refresh | 3,200 | Yes |
| Website launch | 4,800 | Yes |
| Discovery | 1,200 | No |
The example arithmetic is $3,200 + $4,800 = $8,000. That is this client’s planned budget across the two linked projects. An unrelated project elsewhere in the Projects database is outside this calculation. Notion defines Sum over the numeric properties of related pages, so correct membership matters as much as the calculation.
Keep the name honest. A planned-budget total is not paid revenue. A missing budget is also different from an unlinked project: Count empty counts related pages with an empty selected property; it does not find every project that lacks a client.
Configure the rollup on the client
For this small comparison, use existing Clients and Projects databases. Planned budget must be a Number property on Projects. If Clients already has the correct Projects relation, reuse it; adding another connection just for the rollup makes membership harder to inspect.
- If the relation is missing, add a property on Clients, choose Relation, select the Projects database, and finalize with Add relation. In North Studio's relation cell, select Brand refresh and Website launch. Notion's relation setup lets you choose the linked pages; connecting the databases alone does not select every project.
- Add another property on Clients, choose Rollup from the Property type menu, and name it Total planned budget.
- Open a cell in that rollup and choose the Projects relation, the related Planned budget property, and Sum. Select an appropriate number format and decimal placement for your budget display, as described in Notion's rollup configuration. Keep all source amounts in the same currency; display formatting is not a conversion step.
Check one client's linked-page list and the two source amounts before trusting the displayed total. This example should correspond to 8,000, not the database-wide 9,200. If the membership is right but the value differs, inspect the selected source property and calculation. Show unique values and Sum answer different questions. Do not overwrite the source budgets simply to obtain the number you expected.
Check direction and value type
For two different databases, relations are one-way by default. If you create Client in Projects and want the matching Projects relation in Clients, turn on Show on Clients and name the corresponding property. Edits to that two-way relation are reflected on both sides. Do not assume the reverse field already exists.
If each project should have one client, the Client relation can be limited to 1 page. Apply that limit to the project’s client field, rather than limiting the client’s project list to one project.
The source property also limits the calculation. Notion lists Sum and Average for Number properties, and Earliest date and Latest date for Date properties. It also says you cannot directly roll up another rollup. Start from the original value instead of building a chain that relies on that unsupported step.
For the full setup, use the client and project database guide. If an existing result is blank or unexpected, trace the source value, relation, and rollup configuration before changing the model.
