In Excel or Google Sheets, customer retention rate for a whole period is (SUM(Z2:Z7) - SUM(W2:W7)) / SUM(X2:X7), where each SUM covers one column of monthly figures. On the sample data it returns 94.75%.
Retention rate = (Customers at end − New customers) ÷ Customers at start × 100
What you need
Customer retention rate is the percentage of customers at the start of a period who are still customers at the end: customers at the end minus new customers gained, divided by customers at the start, times 100. You need these columns, here from the sample file monthly.csv:
- New subscribers: column W (new_customers)
- Subscribers at start of month: column X (customers_start)
- Subscribers at end of month: column Z (customers_end)
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(Z2:Z7) - SUM(W2:W7)) / 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 =(Z2 - W2) / 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((Z2 - W2) / X2,"").
The formulas
=(SUM(Z2:Z7) - SUM(W2:W7)) / SUM(X2:X7)=(Z2 - W2) / X2What you should get
Run against the sample data, the code above returns these values:
| Month | new_customers | customers_start | customers_end | retention_rate |
|---|---|---|---|---|
| 2026-01 | 120 | 800 | 880 | 95.00% |
| 2026-02 | 135 | 880 | 971 | 95.00% |
| 2026-03 | 150 | 971 | 1,069 | 94.64% |
| 2026-04 | 128 | 1,069 | 1,136 | 94.29% |
| 2026-05 | 160 | 1,136 | 1,239 | 94.98% |
| 2026-06 | 175 | 1,239 | 1,348 | 94.67% |
| Whole period | 868 | 6,095 | 6,643 | 94.75% |
(6,643 − 868) ÷ 6,095 × 100 = 94.75%
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 retention rate misleads
- Take new customers out of the end count, or retention looks higher than it is.
- Reactivated customers (who left and came back in the same period) muddy the count. Decide how to treat them.
- Retention over a year is not monthly retention to the twelfth power if churn changes over the year.
The full explanation, with a calculator, is on the Customer retention rate (CRR) page.
Same metric, other tools
Related metrics in Excel and Google Sheets
Learn more about Excel
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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