Free tool
How long until a customer pays you back
CAC payback is the number of months a customer takes to repay what you spent acquiring them. It is calculated on gross profit rather than revenue, which is the step most people skip. Under twelve months is generally healthy for B2B SaaS, and beyond eighteen it starts constraining growth.
Last reviewed 27 August 2026
Result
Customer acquisition cost
$1,000
Payback period
4.2 months
On gross profit, not revenue
Why margin matters
| Basis | Monthly value | Payback |
|---|---|---|
| Revenue | $300 | 3.3 months |
| Gross profit | $240 | 4.2 months |
Healthy for B2B SaaS. Under twelve months means growth largely funds itself.
How this works
What the numbers mean.
- 01CAC is total sales and marketing spend divided by new customers in the same period. Include salaries and tooling, not just ad spend, or the number flatters you.
- 02Payback divides CAC by monthly gross profit, which is revenue multiplied by gross margin. Using revenue instead of gross profit is the single most common error and it understates payback by whatever your cost of service is.
- 03Compare the two rows in the table. The gap between them is the money that never reaches your bank account.
Assumptions and limits
- This assumes customers stay long enough to reach payback. If your churn is high, payback can be arithmetically fine and commercially impossible.
- Blended CAC across all channels hides a lot. Organic and paid usually differ by an order of magnitude.
- The under-twelve-months guideline is a widely used convention in B2B SaaS, not a law, and it varies with contract length and pricing model.
Questions about this tool
Should I include salaries in CAC?
Yes. Fully loaded sales and marketing salaries, contractor costs, tooling, and ad spend all belong in CAC. Excluding salaries is the most common way companies produce a CAC figure that looks good and predicts nothing.
Why use gross profit instead of revenue?
Because revenue is not money you keep. If your gross margin is 70 percent, only 70 cents of each revenue dollar is available to repay acquisition cost. Calculating on revenue makes payback look roughly a third faster than it is.
What if my payback is over 18 months?
It means growth consumes cash rather than generating it, so you are funding it from investment or reserves. That can be a deliberate choice with a long contract and low churn. It becomes dangerous when it is accidental, which is usually the case when CAC was measured on revenue.
How do organic channels change this?
They usually improve it substantially, because the cost is front-loaded rather than per-customer. Content and community work has a high fixed cost and a near-zero marginal cost, so blended CAC falls as the channel matures. That is the main financial argument for owned channels.
This tool is free and there is nothing to sign up for. If you would rather have the work done than calculate it, that is what Zway does.