How to Calculate Customer Acquisition Cost (CAC)
Customer acquisition cost is total sales and marketing spend for a period divided by the number of new customers acquired in that period. If you spent 12,000 on marketing and sales in a quarter and gained 40 new customers, CAC is 300. The figure is only meaningful when you are consistent about which costs are included — ad spend, agency or freelancer fees, software, and the portion of salaries spent on acquisition — and when you compare it against what a customer is worth over their lifetime rather than on first purchase.
The formula
CAC = total acquisition cost over a period, divided by new customers acquired in that period. The arithmetic is trivial. Every difficulty in practice comes from deciding what goes in the numerator and what counts as a new customer.
Which costs belong in the numerator
The defensible rule: include every cost incurred to win customers, and exclude costs you would incur anyway. Where a cost is shared, apportion it rather than ignoring it.
| Cost | Include? | Note |
|---|---|---|
| Advertising spend | Yes | The obvious one, and rarely the largest |
| Agency, freelancer or contractor fees | Yes | Including retainers, whether or not a campaign ran that month |
| Marketing and sales software | Yes | CRM, email, landing page and analytics tooling |
| Salaries of people doing acquisition work | Yes, apportioned | If someone spends half their time on sales, include half |
| Creative and content production | Yes | Apportion long-lived assets across the periods they serve |
| Delivery and fulfilment costs | No | That is cost of service, not acquisition |
| Rent, accounting, general overhead | No | You would incur it with no marketing at all |
Choosing the period, and the lag problem
Costs and customers rarely land in the same month. If your sales cycle is six weeks, January's spend produces some of February's customers, and a strict monthly CAC will oscillate for reasons that have nothing to do with performance.
Two workable fixes. Use a period comfortably longer than your sales cycle — quarterly for most service businesses. Or offset the comparison, measuring customers won in a period against spend from the period before. Pick one and keep it; the trend matters more than the absolute figure, and switching method destroys the trend.
Blended CAC versus channel CAC
Blended CAC divides all acquisition cost by all new customers, including those who arrived through referral or direct. It tells you the true cost of growth and is the right number for planning.
Channel CAC divides one channel's cost by the customers attributable to it. It tells you where to allocate budget, and it is always somewhat wrong, because attribution is imperfect and channels influence each other. Use both, and do not be surprised when the channel figures do not reconcile neatly to the blended one.
Reading the number: CAC against lifetime value
CAC in isolation is meaningless. A CAC of 400 is excellent if a customer is worth 4,000 over their lifetime and ruinous if they are worth 450. The number that matters is the ratio between customer lifetime value and CAC.
A ratio around 3:1 is widely cited as healthy, and it is a reasonable starting reference — but treat it as a prompt for thinking rather than a target to hit. A very high ratio often means you are underinvesting in growth rather than performing well. A ratio near 1:1 means you are buying customers for roughly what they are worth, which is not a business.
There is one further constraint that ratios hide: payback period. If a customer is worth 4,000 but pays it over three years, and you spend 400 to acquire them today, the ratio is fine and the cash flow may not be. For most owner-operated businesses payback period is the more binding limit.
Run it on your own numbers
The arithmetic above is easy to get wrong under time pressure, which is why we built calculators for it. The CAC calculator handles the apportionment, and the customer lifetime value calculator gives you the other half of the ratio. Both run in the browser and store nothing.
Frequently asked questions
- What is the customer acquisition cost formula?
- Total sales and marketing cost for a period divided by the number of new customers acquired in that period. Include advertising, agency and freelancer fees, marketing and sales software, and the apportioned salary cost of people doing acquisition work.
- Should salaries be included in CAC?
- Yes, apportioned to the share of time spent on acquisition. Excluding them is the most common cause of an artificially low CAC and of scaling a channel that is not actually profitable.
- What is a good CAC to LTV ratio?
- Around 3:1 is a common reference point, meaning a customer is worth roughly three times what it costs to acquire them. Treat it as a prompt rather than a target: a much higher ratio often signals underinvestment in growth, and payback period may constrain you before the ratio does.
- What is the difference between CAC and cost per lead?
- Cost per lead measures the cost of an enquiry; CAC measures the cost of a customer. They diverge by your close rate, so a low cost per lead can coexist with a high CAC if the leads do not convert.
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Customer Acquisition Systems
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