docs/data/reusables/projects/customize/sum.md

You can configure a view to show the sum of one of more number fields, including a count of items in the group or column. For example, if you have a number field tracking the number of hours each item may take to complete, you can display of sum of those hours for each group or column.

In a board layout, field sums are displayed at the top of each column. In table and roadmap layouts, when you enable grouping by a field, field sums are included in each group's header.

{% data reusables.projects.open-view-menu %}

1. Click {% octicon "number" aria-hidden="true" aria-label="number" %} Field sum.
2. Select the fields you want to include.