Counting the real cost
Ad spend alone rarely tells the whole story. A true figure includes creative work, marketing tools and the time people spend on sales. If you do your own selling, put a value on that time. The first few customers from word of mouth can feel free, but they still have a cost once you need to win them on purpose.
It helps to calculate this separately by channel, if you can. A blended figure can hide one strong channel that is carrying a very weak one. Ad platforms report their own numbers, so compare them with the customers who actually show up in your records.
The formulas
CAC
CAC = (Marketing spend + Sales costs) ÷ New customers
Payback
Payback months = CAC ÷ Monthly gross profit per customer
Worked example
A subscription business spent $12,000 on marketing and $3,000 on sales in a month and won 50 new customers, each producing $60 of monthly gross profit.
- Total spend: $15,000.00.
- CAC: $15,000 ÷ 50 = $300.00.
- Payback: $300 ÷ $60 = 5 months.
Payback tells you about cash
Payback shows how long your money is tied up before a customer becomes profitable. A short payback lets you reinvest quickly and grow from your own cash flow, while a long payback needs more funding, even if each customer is profitable in the end. Use gross profit, not revenue, because it reflects what you really keep from each sale.
Pair this with the customer lifetime value calculator to see whether customers stay long enough to justify the cost.
Frequently asked questions
What is a good CAC?
There is no universal figure, because it only means something relative to what a customer is worth to you. A high CAC is fine for clients who stay for years, while a low one can still lose money on one-time buyers.
What about long sales cycles?
If it takes months to win customers, this month's spending may produce next quarter's sales. Use a longer period or offset your spend from your customers by the length of the cycle.
What if I do not sell subscriptions?
Enter nothing in the monthly field and compare CAC directly with the gross profit from a customer's first order and likely repeat orders.
Should I count existing customers who bought again?
No. Count only new customers. Repeat purchases are valuable, but they belong in lifetime value rather than acquisition.