Add Cumulative Sum to Excel Files Online
Add a running total column to Excel files for any numeric column. Optionally order by a date or sequence column and restart totals per group — no upload required.
How to add Cumulative Sum to Excel files
- Drop your file onto the upload area. It is loaded into the in-browser engine and the first 200 rows are shown.
- Choose the value column to sum. Only numeric columns are listed, and the first one is preselected.
- Choose an Order by column, usually a date or sequence number. Leave it at (none) to add up rows in file order, top to bottom.
- Optionally choose a Partition by column so the running total restarts for each group. Rename the output column from cumulative_sum if you like, then click Add Cumulative Sum.
- Check the preview and download the file in the same format you uploaded.
Your file is processed locally in your browser and is never uploaded. The free limit is 50 MB per file; larger files work if your device has the memory for them.
Worked example
A facilities team logs daily solar generation in kWh for two roof arrays. They want month-to-date output for each array, so the running total must restart per site.
Input (Excel)
Excel workbook, first sheet (Sheet1)
| reading_date | site | kwh |
|---|---|---|
| 2026-06-01 | Roof A | 18.5 |
| 2026-06-01 | Roof B | 11 |
| 2026-06-02 | Roof A | 21 |
| 2026-06-02 | Roof B | 9.5 |
| 2026-06-03 | Roof A | 16.5 |
| 2026-06-03 | Roof B | 12.5 |
Settings
- Value column: kwh
- Order by: reading_date
- Partition by: site
- Output column name: cumulative_sum
Result
| reading_date | site | kwh | cumulative_sum |
|---|---|---|---|
| 2026-06-01 | Roof A | 18.5 | 18.5 |
| 2026-06-01 | Roof B | 11 | 11 |
| 2026-06-02 | Roof A | 21 | 39.5 |
| 2026-06-02 | Roof B | 9.5 | 20.5 |
| 2026-06-03 | Roof A | 16.5 | 56 |
| 2026-06-03 | Roof B | 12.5 | 33 |
Each site gets its own running total in date order: Roof A goes 18.5, 39.5, 56 and Roof B goes 11, 20.5, 33. The rows stay in their original order. With Order by and Partition by both left at (none), the total would run down the file instead: 18.5, 29.5, 50.5, 60, 76.5 and 89.
Working with Excel files
Number cells on the first sheet are read as displayed text, so the running total is built from what the cells show. An amount of 19.99 in a whole-number format is read as 20. Over hundreds of rows that rounding adds up. Amounts formatted as currency, such as "$19.99", are read as text and will not appear in the value column list. Set the amounts to General or Number with enough decimals before uploading.
Date cells are read from their stored date, not their display style. A short date like 6/1/26 and a custom style like 1-Jun-26 both load as real dates, so the Order by column follows the calendar. Dates typed as text are the catch. A text column of values like "1-Jun-26" stays VARCHAR and orders alphabetically, so the running total follows the wrong sequence. Run Parse Dates on it first. Excel users often build running totals with a formula like =SUM($C$2:C2). The downloaded Sheet1 holds fixed values instead, which stay correct after you sort or filter the sheet.
Frequently Asked Questions
Why doesn't my Excel running total match the SUM in my workbook?
Cells are read at their displayed precision. If amounts are shown rounded, the tool sums the rounded values. Show full decimals or use General format, then upload again.
Will the output contain a running-total formula?
No. The cumulative column holds plain values. It will not update if you later edit the amounts in Excel.
What does (none) in Order by do?
It adds up rows in file order, top to bottom. With a Partition by column, each group has its own running total, still in file order. Pick a date or sequence column when the file is not already sorted.
How does the total restart for each group?
Choose a Partition by column. The total starts again at the first row of each group value, in Order by order or in file order when Order by is (none). Rows are not regrouped, so they keep their original order.
How are rows with the same Order by value handled?
They are added in file order, one row at a time. The result is the same every time you run it.
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