About the CAC Payback Period Calculator
This CAC payback period calculator shows how long it takes a new customer to repay what you spent acquiring them. Enter customer acquisition cost, the monthly revenue a new customer brings in and your gross margin, and it returns the payback period in months — the number SaaS investors use to judge how cash-efficient growth is.
You can calculate it per customer (CAC ÷ monthly gross profit per customer) or for a whole cohort using last period’s sales and marketing spend and the new MRR it produced. Adding monthly churn gives a more realistic churn-adjusted payback, because some customers cancel before they have paid back their CAC — and if churn is high enough, the cohort never pays back at all.
Payback matters because every month of payback is a month your cash is tied up funding growth. Shorter payback lets you reinvest faster and need less outside capital; long payback can be fine for very sticky enterprise customers but makes growth expensive.
With the default inputs, the cac payback period is 11 mo. Change any value above to recalculate instantly.
How to use the cac payback period calculator
- 1Choose whether to calculate for an average customer or a whole cohort.
- 2Enter CAC and monthly revenue per customer, or period spend and the new MRR it produced.
- 3Enter gross margin so payback uses profit, not revenue.
- 4Add monthly churn to see the churn-adjusted payback.
- 5Compare the result with the 12-month benchmark and check the chart.
Formula and method
Simple CAC payback divides acquisition cost by the monthly gross profit a customer produces. For a cohort, sales and marketing spend for the period replaces CAC and the new MRR it generated replaces revenue per customer — the two methods give the same answer when figures are consistent.
The churn-adjusted version assumes a constant share c of the cohort cancels each month, so cumulative gross profit after n months is GP × (1 − (1 − c)^n) ÷ c. Solving for when that equals CAC gives the formula above. If CAC × c ÷ GP is 1 or more, lifetime gross profit (GP ÷ c) never covers CAC and payback never happens.
- CAC
- Acquisition cost per customer, or total spend for a cohort
- GP
- Monthly gross profit: monthly revenue × gross margin
- c
- Monthly churn rate as a decimal
Worked examples
$1,200 CAC, $150/month, 75% margin
Each customer produces $150 × 75% = $112.50 of monthly gross profit, so $1,200 of CAC is repaid in 10.7 months. With 2% monthly churn some customers leave early and cohort payback stretches to about 11.9 months.
Cohort view: $300k spend, $20k new MRR
Last quarter’s $300,000 of sales and marketing produced $20,000 of new MRR, or $16,000 of monthly gross profit. That takes 18.75 months to repay, or about 20.7 months after 1% monthly churn — slow, though the 5.3:1 LTV:CAC shows the customers are valuable.
High churn that never pays back
At $40 of monthly gross profit a $1,200 CAC would take 30 months to recover, but with 5% monthly churn the average customer only generates $800 of lifetime gross profit — the cohort never pays back.
Frequently asked questions
How do you calculate CAC payback period?+
Divide customer acquisition cost by the monthly gross profit from a new customer (monthly revenue × gross margin). For example, $1,200 ÷ ($150 × 75%) = 10.7 months.
What is a good CAC payback period?+
Under 12 months is widely considered good for SaaS, and under 6 months is excellent, especially for SMB customers who churn faster. Enterprise companies with very low churn often accept 18–24 months or more.
Why use gross margin instead of revenue?+
Revenue is not all available to repay acquisition cost — hosting, support and payment fees come out first. Using gross profit shows when the customer has genuinely covered what you spent to win them.
What is the difference between CAC payback and LTV:CAC?+
Payback measures speed — how many months until you break even on a customer. LTV:CAC measures total return over the customer’s life. A business can have a strong LTV:CAC but a long payback that requires a lot of cash upfront.
How can I shorten CAC payback?+
Lower CAC through better conversion and cheaper channels, raise starting prices or push annual prepaid plans, improve gross margin, and reduce early churn with better onboarding so more customers stay long enough to pay back.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.