CAC payback period is the number of months it takes for a new customer's gross profit to repay what you spent to acquire them. If winning a customer costs $1,200 and they bring in $80 of gross profit a month, CAC payback is 15 months.
In SaaS it is the most practical efficiency check, because it measures how long cash is tied up in each new customer before growth starts paying for itself.
The CAC payback formula
Per customer:
CAC payback (months) = CAC / (new MRR per customer × gross margin %)
Company level, for a period such as a quarter:
CAC payback (months) = sales and marketing spend in the period
/ (new MRR added in the period × gross margin %)Both versions give the same answer when the inputs agree. The company-level version is easier to keep up to date, because it needs only three numbers that your accounts and billing system already have.
A worked CAC payback calculation
Per customer:
| Input | Value |
|---|---|
| CAC | $1,200 |
| New MRR per customer | $100 |
| Gross margin | 80% |
monthly gross profit per customer = 100 × 0.80 = $80 CAC payback = 1,200 / 80 = 15 months
Company level, for the third quarter:
| Input | Value |
|---|---|
| Sales and marketing spend | $90,000 |
| New MRR added (75 new customers at $100) | $7,500 |
| Gross margin | 80% |
CAC payback = 90,000 / (7,500 × 0.80) = 90,000 / 6,000 = 15 months
Fifteen months means every customer won this quarter is a net cost to the company until the end of next year. If 2% of customers churn each month, about a quarter of them will have left before they pay back, which is why payback and churn have to be read together.
What counts as a good CAC payback
David Skok's "SaaS Metrics 2.0" guide (forEntrepreneurs, first published 2014) suggests that months to recover CAC should be under 12. He notes that enterprise businesses that land with a small first deal and expand later can reasonably run around 20 months, since the account keeps growing after the first sale. He also links it to sales efficiency: ignoring gross margin, a magic number of 1 means about 12 months to recover CAC.
How to shorten CAC payback
- Raise revenue per new customer with higher entry tiers or per-seat pricing. Annual prepayment helps cash payback, not this metric.
- Lower CAC by moving spend to the channels with the lowest CAC per customer and dropping the rest.
- Improve gross margin so more of each dollar goes toward payback.
- Reduce early churn with better onboarding, since a customer who leaves at month eight never pays back.
Common CAC payback mistakes
- Leaving out gross margin. It shortens payback by 20% or more for a typical software company.
- Dividing by total MRR instead of new MRR. The existing base wasn't bought with this quarter's spend.
- Adding expansion MRR to new MRR without saying so. Some teams do, which is fine if you say so, but it flatters payback in a strong upsell quarter.
- Ignoring the sales cycle. If deals take three months to close, compare spend with new MRR one quarter later.
- Using paid-media CAC only. Salaries and tools are part of acquisition cost.
Related metrics
- CAC: what goes into acquisition cost.
- LTV to CAC ratio: how much a customer returns in total, not how fast.
- SaaS magic number: new ARR per dollar of sales and marketing, closely tied to payback.
- Burn multiple: the cash cost of growth at company level.
Get CAC payback automatically
New MRR comes from billing and spend from your books. The Stripe weekly MRR report posts new MRR every Monday as one of the four movements of net new MRR, and QuickBooks expenses by category posts spend by expense account. Have your agent add up a quarter of each, apply your gross margin and post CAC payback as a metric card at the start of every quarter, so the trend builds up without a spreadsheet.
Questions
What is a good CAC payback period?
David Skok's SaaS Metrics 2.0 guideline is under 12 months. He notes that enterprise businesses that land small and expand can reasonably run around 20 months, because existing customers grow after the first sale.
Should CAC payback use gross margin?
Yes. Revenue that goes straight out again in hosting, support and payment fees can't repay acquisition. Without the gross margin adjustment the payback looks shorter than it is.
What is the difference between CAC payback and LTV to CAC?
Payback measures speed: months until a customer has earned back their cost. LTV to CAC measures size: how many times over they earn it in total. A business needs both to look healthy.
Does an annual prepayment shorten CAC payback?
It shortens the cash payback, since the money arrives on day one, but not the standard metric, which is based on monthly gross profit. Report cash payback separately if prepayments are common.