How to Calculate Customer Acquisition Cost (CAC)
Customer acquisition cost (CAC) measures how much you spend to win each new customer. It is a core unit-economics metric for marketing and growth because it connects acquisition spending to actual customers, not just clicks or leads. This guide explains the formula, a worked example, what to include, and how to interpret CAC alongside lifetime value.
Last reviewed: 2026-08-26
Customer acquisition cost formula
- CAC = Total Customer Acquisition Costs ÷ New Customers Acquired
The numerator should contain the sales and marketing costs used to acquire customers during the period you are measuring. The denominator should contain new customers acquired during that same period. Matching the time period and scope is essential: dividing one quarter of spending by one month of customers produces a misleading result.
Worked CAC example
Suppose a business spends $8,000 on advertising, $2,500 on agency and software costs, and $1,500 on acquisition-related sales commissions during a month. It acquires 300 new customers.
- Total acquisition costs = $8,000 + $2,500 + $1,500 = $12,000
- CAC = $12,000 ÷ 300 = $40 per customer
The average acquisition cost is $40 for each new customer. You can test your own numbers with the Customer Acquisition Cost Calculator.
What should you include in CAC?
The answer depends on the scope of the metric. A fully loaded CAC can include paid media, sales commissions, agency fees, marketing and sales software, creative production, and relevant employee costs. A channel-level CAC may include only costs attributable to that channel. Neither approach is automatically wrong, but comparisons are only meaningful when the cost definition stays consistent.
Avoid quietly changing the numerator. If one month includes salaries and software while another includes ad spend only, the apparent CAC improvement may come from accounting rather than better acquisition performance.
CAC vs CPA: they are not always the same
Cost per acquisition (CPA) is often used for a platform-defined conversion such as a lead, trial, app install, signup or purchase. CAC is narrower: the outcome is a new paying customer. If an ad campaign generates 500 leads but only 100 become customers, dividing spend by 500 measures cost per lead, not customer acquisition cost.
How conversion rate affects CAC
CAC can fall even when traffic costs stay unchanged if more prospects become customers. For example, improving a landing page or checkout flow can turn the same advertising spend into more customers, reducing CAC. Use the Conversion Rate Calculator to measure the percentage of visitors or leads completing the target action.
How to judge whether your CAC is sustainable
A CAC number is not good or bad by itself. A $100 CAC can be excellent if a customer generates hundreds of dollars of contribution over time, and unsustainable if the first purchase produces only $20 of gross profit with little repeat business. Compare acquisition cost with customer economics rather than with a generic industry benchmark.
The Customer Lifetime Value Calculator can help estimate the value of a customer over time. The gap between value and acquisition cost must also leave room for product costs, fulfillment, support, overhead, refunds and profit.
CAC and ROAS answer different questions
ROAS measures revenue attributed to advertising relative to ad spend, while CAC measures acquisition cost per new customer. A campaign can improve ROAS because customers spend more without changing the number of customers acquired, or improve CAC by acquiring more customers at the same spend. Track both when you need to understand revenue efficiency and customer acquisition efficiency. Calculate campaign return with the ROAS Calculator.
Common CAC mistakes
- Mixing new and returning customers. CAC is intended to measure the cost of acquiring new customers; including repeat buyers can make acquisition look cheaper than it is.
- Using mismatched periods. Costs and acquired customers should cover the same measurement window.
- Ignoring delayed conversions. Long sales cycles can make a single month misleading because spending today may create customers later.
- Comparing inconsistent cost definitions. Decide whether you are measuring paid-media CAC, channel CAC or fully loaded CAC before comparing results.
- Optimizing CAC without checking customer quality. A cheaper customer is not necessarily more valuable if retention, order value or margin falls.
A practical way to monitor CAC
Track CAC on a consistent cadence, keep the formula definition documented, and segment it only when the underlying data supports a fair comparison. Then read CAC together with conversion rate, customer lifetime value, margin and payback. That combination shows whether growth is becoming more efficient or simply cheaper at the top of the funnel.