CAC Payback Period Calculator: Months to Earn Back Acquisition Cost

How it is calculated.

CAC = sales and marketing spend / new customers won in the same period.
Monthly gross profit per customer = monthly revenue per customer x gross margin.
CAC payback = CAC / monthly gross profit per customer.
First-year ratio = 12 x monthly gross profit / CAC; above 1x means a customer repays its cost within a year.

Worked example.

60 new customers in a quarter

Step	Working
CAC	$300,000 / 60 = $5,000
Gross profit per month	$1,000 x 75% = $750
CAC payback	$5,000 / $750 = 6.7 months
First-year ratio	12 x $750 / $5,000 = 1.8x

Why gross margin belongs in it.

Revenue is not what pays back acquisition cost; gross profit is. A company with 40% margins needs nearly twice as long to earn back the same CAC as one with 75% margins, which is why investors prefer the margin-adjusted version.

Rough ranges.

For subscription software, payback under 12 months is often described as strong, 12 to 18 months as typical and above 24 months as a concern. Enterprise sales cycles and contract sizes support longer paybacks than self-serve products, so compare with companies that sell the way you do.

Use it with retention.

A short payback means little if customers leave before it ends. Pair this number with net revenue retention: a customer that expands after year one makes a longer payback acceptable, and one that churns at month eight turns a seven-month payback into a thin return.

Common mistakes.

Leaving sales salaries and tools out of spend and counting only ad budgets.
Dividing by all new customers, including ones that came from referrals with no acquisition cost, without saying so.
Using revenue instead of gross profit.
Matching spend from one month with customers that closed months later in a long sales cycle.

Questions founders ask

What is a good CAC payback period?

For subscription software, under 12 months is generally seen as strong and 12 to 18 months as acceptable. Longer paybacks can work for enterprise contracts with high retention.

Should CAC be blended or paid only?

Show both if you can. Blended CAC includes organic customers and looks better; paid CAC shows what growth costs once you spend to get it. Investors usually ask which one you are quoting.

How is this different from LTV to CAC?

Payback tells you how fast cash comes back; LTV to CAC tells you how much comes back over the whole customer life. Payback relies less on churn assumptions, which makes it harder to inflate.