CAC Payback Period: Formula, Example and Excel Calculation

CAC payback period formula

CAC payback (months) = CAC ÷ (Average new MRR per customer × Gross margin %)

• CAC: Sales and marketing cost for the period ÷ new customers acquired in the period.
• Average new MRR per customer: Monthly recurring revenue added by an average new customer at signup.
• Gross margin: Subscription gross margin as a decimal: the share of revenue left after hosting, support and other cost of revenue.

How to calculate CAC payback period in Excel and Google Sheets

Excel, using the cells in the worked example below:

=(B2/B3)/(B4*B5)

Worked example

A marketing-automation SaaS company wants Q3 CAC payback to decide whether it can afford to double paid acquisition next year.

1. CAC = 612,000 ÷ 180 = $3,400.
2. Monthly gross profit per new customer = 410 × 0.78 = $319.80.
3. Payback = 3,400 ÷ 319.80 = 10.6 months.
4. On revenue rather than gross profit it would be 3,400 ÷ 410 = 8.3 months, which looks better than reality.

Result: 10.6 months CAC payback

How to interpret CAC payback period

Payback is a cash-efficiency measure: the shorter it is, the faster acquisition spend comes back to fund more growth. Many SaaS operators treat roughly 12 months or less as healthy for SMB products and accept longer paybacks, sometimes 18–24 months or more, for enterprise contracts with strong retention. Payback only works if customers stay longer than the payback period, so read it next to churn: a 10-month payback with 5% monthly churn means a meaningful share of customers leave before they've paid back.

Common mistakes

• Using revenue instead of gross profit, which shortens payback by the size of your cost of revenue.
• Ignoring churn during payback. If many customers leave before month 10, true payback is longer than the formula says.
• Mixing periods: Q3 spend divided by Q3 customers when the sales cycle is three months long. Lag spend or use trailing twelve months.
• Using blended new MRR when segments differ a lot. Calculate payback per segment or channel.

Calculate CAC payback period with Better Analyst

Connect your data or upload a spreadsheet, then ask in plain English. Better Analyst writes and runs the calculation and shows the steps, so you can check the number.

• “Calculate CAC payback by quarter and by acquisition channel for the last two years.”
• “How does payback change if gross margin rises to 82%?”
• “Show the share of each signup cohort still active at the month payback is reached.”

Usually calculated from: PostgreSQL, Google BigQuery, Snowflake, Google Sheets, Supabase.

Try Better Analyst free

Further reading

• How to calculate CAC
• How to calculate churn rate
• Burn rate formula
• How to divide in Excel