In Excel or Google Sheets, customer churn rate for a whole period is SUM(Y2:Y7) / SUM(X2:X7), where each SUM covers one column of monthly figures. On the sample data it returns 5.25%.
Customer churn rate = Customers lost during the period ÷ Customers at the start of the period × 100
What you need
Customer churn rate is the percentage of customers you had at the start of a period who left during it: customers lost divided by customers at the start, times 100. You need these columns, here from the sample file monthly.csv:
- Subscribers at start of month: column X (customers_start)
- Subscribers who cancelled: column Y (customers_churned)
Step by step
- Download monthly.csv below and open it: in Excel use File → Open; in Google Sheets use File → Import → Upload. The headers land in row 1 and the six months in rows 2 to 7.
- Click any empty cell and enter =SUM(Y2:Y7) / SUM(X2:X7) for the whole six months. It adds up each column first and then does the arithmetic once, which is the correct way to combine months.
- For each month, click AQ2, enter =Y2 / X2 and drag the fill handle down to row 7.
- Format the results as a percentage (Home → %, or Format → Number → Percent in Sheets). The formula returns a fraction such as 0.45, which the format shows as 45%.
- If a month can have zero in the denominator, wrap the formula so it shows a blank instead of #DIV/0!: =IFERROR(Y2 / X2,"").
The formulas
=SUM(Y2:Y7) / SUM(X2:X7)=Y2 / X2What you should get
Run against the sample data, the code above returns these values:
| Month | customers_start | customers_churned | churn_rate |
|---|---|---|---|
| 2026-01 | 800 | 40 | 5.00% |
| 2026-02 | 880 | 44 | 5.00% |
| 2026-03 | 971 | 52 | 5.36% |
| 2026-04 | 1,069 | 61 | 5.71% |
| 2026-05 | 1,136 | 57 | 5.02% |
| 2026-06 | 1,239 | 66 | 5.33% |
| Whole period | 6,095 | 320 | 5.25% |
320 ÷ 6,095 × 100 = 5.25%
Notes for Excel
- Google Sheets accepts the same formulas. If your spreadsheet locale uses a comma as the decimal separator, Sheets and Excel expect semicolons between function arguments instead of commas.
- Averaging the monthly results with AVERAGE() gives a different and usually wrong answer for the period, because every month counts the same however large it was.
- Excel tables (Insert → Table) let you write the same formula with column names instead of letters, which is easier to read and survives inserted columns.
Where customer churn rate misleads
- Do not include customers who joined during the period in the denominator; they were not there at the start.
- Six monthly churn rates averaged is not the same as churn over six months. Over the whole period here, churned customers are divided by the sum of monthly starting customers, which gives an average monthly rate.
- For one-off purchase businesses, "churn" needs a definition (no order in 90 days, say). Pick one and keep it.
The full explanation, with a calculator, is on the Customer churn rate page.
Same metric, other tools
Related metrics in Excel and Google Sheets
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About the data on this page
The figures come from a small made-up dataset, printed above in full so you can check every number by hand. Download it as monthly.csv. The results are computed from those rows when the page is built, and the Excel formulas, SQL and Python on these pages are run against the same rows before publishing, so the code and the answers agree.
To get these numbers from your own data without writing formulas, try AnalyzeIt: ask in plain words and it shows the working behind every figure.
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