# How to calculate cumulative percentage in Excel

Divide a running total by the grand total: `=SUM($B$2:B2)/SUM($B$2:$B$8)`, filled down.

**Excel:** `=SUM($B$2:B2)/SUM($B$2:$B$8)` (Every current version)

**Google Sheets:** the same formula works.

## Example

Sample data (row 1 is the header):

| A | B | C |
| --- | --- | --- |
| Defect | Count | Cumulative % |
| Scratches | 145 |  |
| Dents | 98 |  |
| Misaligned labels | 61 |  |
| Loose screws | 40 |  |
| Wrong color | 27 |  |
| Missing parts | 18 |  |
| Other | 11 |  |

Formula in C2, filled to C8: `=SUM($B$2:B2)/SUM($B$2:$B$8)`

Result: 36.3%; 60.8%; 76.0%; 86.0%; 92.8%; 97.3%; 100.0%

## How it works

`SUM($B$2:B2)` is a running total: its start is locked and its end moves down a row at a time. Dividing by the fully locked grand total, 400, turns it into a cumulative share that ends at 100%.

Sorted from the biggest category down, as here, this is a Pareto analysis: the top two defect types make up 60.75% of all defects.

## Other ways

- `=B2/SUM($B$2:$B$8)`: Each row's own share, not the running share. (Shows each defect's share separately, such as 24.5% for dents.)
- `=SUM(B$2:B2)/SUM(B$2:B$8)`: Locking only the rows is enough when you fill down one column.

## Common mistakes

- Without sorting from largest to smallest first, the cumulative curve doesn't show which few categories matter most.
- Locking both ends of the running total (`$B$2:$B$2`) or neither end breaks it. Lock only the start.
- If the grand total isn't locked, it shrinks as you fill down and the percentages climb past 100%.

## Questions

**How do I find the categories that make up 80%?**

Flag them with `=C2<=80%`, or include the one that crosses 80% with `=C2-B2/SUM($B$2:$B$8)<80%`.

**How do I make a Pareto chart?**

Select the categories and counts and insert a Pareto chart (Insert, Statistic chart), or combine a column chart with the cumulative % on a secondary axis.

**Which category takes the total past 80%?**

`=XLOOKUP(0.8,C2:C8,A2:A8,,1)` returns the first category whose cumulative percentage is at or above 80%.

Every formula and result on this page was checked by running it in the Spreadsheet Practice formula engine on 2026-10-30.

Source: https://spreadsheetpractice.com/formulas/cumulative-percentage