The calculation, done honestly
CAC payback is fully loaded sales and marketing spend for a period, divided by the gross profit added by the new customers that spend acquired, expressed in months.
Two choices decide whether the answer is meaningful. First, gross profit rather than revenue: a company with 55% margins and a stated twelve-month payback is actually at twenty-two months. Second, fully loaded acquisition cost: salaries, commission, tooling and the share of content and brand spend that supports acquisition, not just paid media.
What counts as good
There is no universal threshold, but the shape of the answer is consistent across business models: the shorter the payback, the less external capital growth consumes. Judge the number against contract length and churn rather than against a benchmark table.
| Payback on gross profit | What it implies | Reasonable when |
|---|---|---|
| Under 12 months | Growth is close to self-funding | Self-serve or short sales cycle |
| 12-24 months | Workable with capital and low churn | Annual contracts, mid-market |
| Over 24 months | Every new customer is a financing decision | Enterprise with multi-year retention |
Where the number gets flattered
- Counting only paid media and excluding the sales team.
- Using bookings rather than cash collected when payment terms stretch.
- Blending expansion revenue from existing customers into new-customer gross profit.
- Averaging across segments when one channel pays back in four months and another never does.
The follow-up question that matters more
Payback tells you how long capital is tied up. It does not tell you whether the customer stays long enough to repay it twice. Pair payback with net revenue retention: a twenty-month payback with 120% net retention is a good business, and a ten-month payback with 70% net retention is a treadmill.
You can model both sides in the free runway calculator, which shows when acquisition spend at a given payback period actually runs the company out of cash.
Part of a guide
Startup financials: unit economics, runway and valuation
A guide to the financial questions that decide early-stage outcomes: CAC, LTV and payback, burn rate and runway, how much runway to hold, and how pre-revenue companies get valued.