Pivot table running total
Pivot tables have a built-in feature to calculate running totals. In the example shown, a pivot table is used group data by month and show both the monthly total and running total over a 6-month period.
The source data contains three fields: Date, Sales, and Color. Only two fields are used to create the pivot table: Date and Sales.
The Date field has been added as a Row field, then grouped by Months:
The Sales field has been added twice as a Value field. The first instance is a simple sum, and has been renamed "Total":
The second instance is renamed "Running" and set to calculate a running total based on the Date field:
Helper column alternative
This example uses automatic date grouping. As an alternative, you can add a helper column to the source data, and use a formula to extract the month name. Then add the Month field to the pivot table directly.