CAC Payback Period Calculator
Work out how many months a new customer takes to pay back their acquisition cost once churn shrinks the cohort, next to the simple payback most dashboards show.
- Free
- No sign-up to try
- Works as you type
CAC payback with churn
Payback with churn
20.2 mo
Simple payback, ignoring churn
16.0 mo
Share of the cohort still paying at payback
59.9%
Share of CAC recovered in the first 12 months
65%
- Monthly gross profit per customer = revenue per account × gross margin.
- Churn shrinks the cohort each month, so after n months it has earned gross profit × (1 − (1 − churn)^n) ÷ churn per customer acquired.
- Payback with churn is the n where that equals CAC: n = ln(1 − CAC × churn ÷ gross profit) ÷ ln(1 − churn). If CAC × churn is at least the monthly gross profit, it never pays back (n/a).
- The formula language has no logarithm, so ln x is worked out as (x^h − x^−h) ÷ 2h with h = 0.0001; tests check it against an exact logarithm.
- Simple payback = CAC ÷ monthly gross profit, the figure most dashboards show.
Free, no sign-up to try. Save it as a live calculator you can share; an estimate from the numbers you enter, not financial advice. Check the result against your own records before you rely on it.
How it works
How the CAC Payback Period Calculator works
- 1
Enter your numbers
Every result updates as you type, with the formula shown under it.
- 2
Check the method
See how each number is worked out and what it assumes.
- 3
Save it as a Room
Share a live calculator: others can change the numbers and see the result update.
Worked example
What it makes
Example inputs
- Cost to acquire a customer (CAC)
- $1,500
- Revenue per account per month
- $120
- Gross margin
- 78 %
- Monthly customer churn
- 2.5 %
Results
- Payback with churn
- 20.2 mo
- Simple payback, ignoring churn
- 16.0 mo
- Share of the cohort still paying at payback
- 59.9%
- Share of CAC recovered in the first 12 months
- 65%
How it's calculated
- Monthly gross profit per customer = revenue per account × gross margin.
- Churn shrinks the cohort each month, so after n months it has earned gross profit × (1 − (1 − churn)^n) ÷ churn per customer acquired.
- Payback with churn is the n where that equals CAC: n = ln(1 − CAC × churn ÷ gross profit) ÷ ln(1 − churn). If CAC × churn is at least the monthly gross profit, it never pays back (n/a).
- The formula language has no logarithm, so ln x is worked out as (x^h − x^−h) ÷ 2h with h = 0.0001; tests check it against an exact logarithm.
- Simple payback = CAC ÷ monthly gross profit, the figure most dashboards show.
- Assumes: Churn is the same every month and counts customers, not revenue; expansion revenue is not included.
- Assumes: Customers pay from their first month and leave at the end of a month.
An estimate from the numbers you enter, not financial advice. Check the result against your own records before you rely on it.
Who it's for
Who uses it
SaaS founders
See whether churn stretches payback past your runway.
Finance and RevOps
Show why simple payback flatters high-churn segments.
Growth teams
Check how far churn can rise before CAC never pays back.
Good to know
What to consider
- With churn, payback is longer than CAC ÷ monthly gross profit, and if churn is high enough it never arrives.
- Churn is treated as the same every month; expansion revenue is not included.
Questions
About the CAC Payback Period Calculator
How is this different from the LTV to CAC calculator?
That one shows simple payback: CAC ÷ monthly gross profit. This one lets the cohort shrink by your churn rate each month, so it shows when the customers you won actually earn back what you spent.
Can I share the calculator with my team or a client?
Yes. The Room keeps the calculator live: anyone with the link can change the numbers and see the result update, with the method and assumptions on the same page.
Make your calculator now
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Related tools
- SaaS LTV to CAC CalculatorWork out customer lifetime value, your LTV to CAC ratio and CAC payback from four numbers, then share it as a live calculator.
- CAC CalculatorWork out your customer acquisition cost two ways: blended CAC across all sales and marketing spend, and paid CAC from ad spend alone.
- Churn Rate CalculatorWork out customer churn and retention for a period from two numbers.