In Excel or Google Sheets, customer acquisition cost for a whole period is SUM(G2:G7) / SUM(W2:W7), where each SUM covers one column of monthly figures. On the sample data it returns ₹771.89.
CAC = Marketing spend ÷ New customers acquired
What you need
Customer acquisition cost (CAC) is how much you spend on marketing to win one new customer: marketing spend in a period divided by the number of new customers in the same period. You need these columns, here from the sample file monthly.csv:
- Marketing spend: column G (marketing_spend)
- New subscribers: column W (new_customers)
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(G2:G7) / SUM(W2:W7) 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 =G2 / W2 and drag the fill handle down to row 7.
- Format the results as currency with two decimals.
- If a month can have zero in the denominator, wrap the formula so it shows a blank instead of #DIV/0!: =IFERROR(G2 / W2,"").
The formulas
=SUM(G2:G7) / SUM(W2:W7)=G2 / W2What you should get
Run against the sample data, the code above returns these values:
| Month | marketing_spend | new_customers | cac |
|---|---|---|---|
| 2026-01 | 96,000 | 120 | ₹800.00 |
| 2026-02 | 1,02,000 | 135 | ₹755.56 |
| 2026-03 | 1,18,000 | 150 | ₹786.67 |
| 2026-04 | 99,000 | 128 | ₹773.44 |
| 2026-05 | 1,24,000 | 160 | ₹775.00 |
| 2026-06 | 1,31,000 | 175 | ₹748.57 |
| Whole period | 6,70,000 | 868 | ₹771.89 |
₹6,70,000 ÷ 868 = ₹771.89
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 acquisition cost misleads
- Count only new customers. Dividing by all orders gives cost per order, which is much lower and flatters the ads.
- Decide whether salaries, agencies and tools count as spend. Including them gives a fully loaded CAC.
- Spend and the customers it brings fall in different months. Compare over a quarter if your sales cycle is long.
The full explanation, with a calculator, is on the Customer acquisition cost (CAC) page.
Same metric, other tools
Related metrics in Excel and Google Sheets
- How to calculate LTV to CAC ratio in Excel and Google Sheets
- How to calculate CAC payback period in Excel and Google Sheets
- How to calculate cost per order in Excel and Google Sheets
- How to calculate marketing efficiency ratio in Excel and Google Sheets
- How to calculate customer lifetime value 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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