CAC is a number many people calculate wrongly, and always in the same direction: too low. The reason is simple, they add up the ad budget and forget everything else, starting with their own time.
An understated CAC produces an imaginary Gross margin and permits investment decisions that do not hold.
Definition
CAC, customer acquisition cost, is the sum of all acquisition spending over a period divided by the number of new customers won in that same period.
"All spending" means all. Advertising, marketing tools, Affiliate marketing commissions, outsourced content, and the cost of your own time spent selling. That last item is the most frequently omitted, and often the heaviest for a Solopreneur.
The honest calculation
Take a real month. You spend €300 on ads, €40 on tools, and put eight hours into writing and answering prospects. Valuing your hour at €60, that is €480 of time.
Total: €820. For twelve new customers, CAC is €68, not €25 as the ad budget alone would suggest.
That difference is not cosmetic: it decides whether your LTV/CAC ratio is healthy, and therefore whether you can accelerate or need to slow down.
CAC varies enormously by channel
| Channel | Money cost | Time cost | Delay |
|---|---|---|---|
| Organic traffic | None | Very high | 6 to 12 months |
| Paid advertising | High | Low | Immediate |
| Cold email | Low | High | Weeks |
| Referral | None | None | Not steerable |
| Affiliate marketing | Variable, performance-based | Low | Immediate |
A global CAC hides those gaps. Calculate it per channel, or you will never know which one to stop.
What lowers it durably
Only three levers, and none is fast:
- A better Conversion rate. The same traffic producing more customers divides CAC accordingly.
- A sharper Value proposition. It reduces the persuasion needed at every step.
- Referral. The only zero-cost channel, earned through Retention rather than marketing.
Frequently asked questions
Should I count my time when working alone?
Yes, absolutely, or your business looks profitable only because a salary is missing from the maths. Value your hour at what you would bill as a freelancer: that is the real opportunity cost.
What CAC is acceptable?
There is no good CAC in the abstract, only CAC relative to LTV (customer lifetime value). A €300 CAC is excellent for a customer worth €3,000 and catastrophic for one worth €200.
How do I treat customers who arrived on their own?
They belong in the calculation, in the denominator. Excluding them would artificially inflate your CAC. Do track their share though: if it rises, your overall CAC falls with no extra effort, and that is the best signal there is.
Over what period should I calculate it?
Monthly to follow the trend, quarterly to decide. A month is too noisy at small volumes, and an investment decision made on an exceptional month gets paid for over the next three.