Know your max ad spend per customer
Stripe, App Store, etc.
After cost to serve (hosting, support)
% of customers who cancel / month
Months to recover ad spend
Landing page conversion
Max you can pay to acquire a paying customer
$145
to break even within 6 months · up to $484 over the full customer lifetime
Healthy CAC (3:1)
$161
Max cost / trial signup
$36
Max cost / click (CPC)
$4
How retention changes your max CAC
| Scenario | Churn | Lifetime | LTV | Max CAC (3:1) |
|---|---|---|---|---|
| Conservative | 8.0% | 13 mo | $303 | $101 |
| Realistic | 5.0% | 20 mo | $484 | $161 |
| Optimistic | 3.0% | 33 mo | $808 | $269 |
If Meta/Google CPCs in your niche exceed $4, paid acquisition won't be profitable at these conversion rates — improve landing page conversion, raise price, or cut churn first.
Max CAC (target payback)
The most you can pay per paying customer and still recover it within your chosen payback window. We use net monthly revenue × payback months. Stay under this to protect cash flow.
Max CAC (lifetime)
The absolute ceiling — total gross profit a customer brings over their lifetime. Spending up to here breaks even eventually, but ties up cash for a long time.
Max cost per trial / signup
Ad platforms optimize toward signups, not paying customers. This is the most you can pay per trial: max CAC × your trial→paid conversion rate.
Max CPC
The most you can pay per ad click given your funnel. If real-world CPCs are higher, the math only works by improving conversion, price, or retention.
You've got the numbers — now ship the features that move them. We help founders scale their app or SaaS with new features, performance, and growth experiments. No bloated retainers, just fast execution.