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CAC (Customer Acquisition Cost), or customer acquisition cost, is the average amount a business must spend to gain one new customer. It is calculated by dividing total sales and marketing costs by the number of new customers in the same period, helping businesses know how much they are paying for a customer and whether they are still profitable.
Key Takeaways
- Formula: CAC = (Marketing costs + Sales costs) ÷ New customers, measured over the same period.
- These costs include ad spend, marketing and sales salaries, tool fees, outsourcing fees — not just ad spend.
- CAC only matters when viewed alongside LTV: an LTV/CAC ratio of 3 or higher is usually considered healthy, while below 1 means the more you sell, the more you lose.
- Payback time matters just as much as the CAC number: recovering costs in 3–6 months is far easier than in 18 months.
- Common mistakes: counting only ad spend, mixing existing customers with new ones, comparing CAC with companies in other industries, and cutting budgets too quickly when CAC rises seasonally.
What is CAC? CAC (Customer Acquisition Cost), or customer acquisition cost, is the average amount a business must spend to gain one new customer. It is calculated by dividing total sales and marketing costs by the number of new customers in the same period, helping businesses know how much they are paying for a customer and whether they are still profitable.
A Detailed Definition of CAC
CAC answers a very practical question: how much money do you spend to get one person to open their wallet? If last month you spent 100 million VND on marketing and sales and brought in 50 new customers, your CAC is 2 million VND per customer. That number is not absolutely right or wrong — it only matters when compared with how much value a customer brings you.
One place many people get the calculation wrong is the “cost” part. CAC is not just the money loaded into your ad account. It includes everything you spend to attract customers: ad budgets, salaries and bonuses for both marketing and sales teams, agency or freelancer fees, the cost of tools such as email, CRM, and design, plus content production costs. Leaving out salaries and tool fees is the fastest way to create a CAC number that looks better than reality.
The second point is “new customers.” Only count first-time buyers, not repeat buyers. If you include existing customers in the denominator, CAC will drop very low and you may think every channel is effective. For the same reason, CAC should be separated by channel — Facebook Ads, Google Ads, SEO, referrals — because each channel has a very different cost and requires a different approach.
Why CAC Matters to a Business
CAC is the line between growth and burning cash. Revenue can double and still be bad news if customer acquisition costs triple. By looking at CAC, you can tell whether you are scaling because your product is strong or because you are buying customers at an ever-higher price.
Read more: What is customer LTV and how to read it correctly
The most useful way to use CAC is to place it next to LTV — the total amount a customer brings in over the time they stay with you. The LTV/CAC ratio shows how many dollars you get back for every dollar spent:
- Below 1: the more you sell, the more you lose; you need to stop and review pricing or acquisition channels.
- Around 1–3: profitable but thin, and easy to turn negative when ad costs rise.
- 3 or higher: usually considered healthy, with enough room to reinvest.
- Above 5: sounds great, but it is often a sign you are spending too little and missing growth opportunities.
Beyond the ratio, look at payback time: how long it takes for a customer to return enough money to cover what you spent to acquire them. With the same 2 million VND CAC, recovering it in 3 months and recovering it in 18 months are two completely different cash-flow problems.
CAC Formula and How to Apply It
CAC = (Marketing costs + Sales costs) ÷ New customers
Three steps to get a usable number. First, lock in the time period and keep it the same for both numerator and denominator, usually by month or by quarter. Second, add up all costs: ad budgets, marketing and sales salaries, agency fees, tool fees, content and image production costs. Third, count the number of first-time buyers in that exact period.
Example: an online fashion store spent 60 million VND on ads in August, 25 million VND on the salaries of two marketing staff, and 5 million VND on tools and design, and brought in 120 first-time buyers. CAC = 90 million VND ÷ 120 = 750,000 VND per customer. If the average order value is 900,000 VND and gross margin is 40%, each first order generates only 360,000 VND in gross profit — meaning the store loses money on the first order and only becomes profitable if the customer buys a second or third time.
That is exactly why CAC rarely stands alone. When CAC is higher than the gross profit from the first order, the question shifts from “how do we get more customers?” to “how do we get customers to come back?”, because the profit is in the second purchase and beyond.
There are two ways to bring CAC down, and the second one is often overlooked:
- Reduce input costs: turn off weak ad sets, tighten targeting, shift budget to the channel with the lowest CAC, and increase the share of unpaid channels such as SEO, email, and referrals.
- Increase conversion rate: if the same amount of traffic converts into more sales, CAC automatically falls. Improving landing pages, shortening checkout steps, and replying to messages faster are often much cheaper than buying more impressions.
- Extend customer lifetime: this does not make CAC smaller, but it improves the LTV/CAC ratio, and that is the number that really matters.
Read more: What is a good ROAS? How to measure effectiveness
Real-World Examples in the Vietnamese Market
A household-goods shop on Shopee spent 40 million VND on ads in a month, plus 15 million VND in salaries and operating costs, and gained 200 new customers. CAC was 275,000 VND. With an average order value of 450,000 VND and a gross margin of 35%, each first order generated about 157,000 VND in profit — not enough to cover CAC. But the data showed that 45% of customers bought again within six months, so over the full lifetime it was still profitable. The takeaway is not to cut ads, but to make sure repeat purchase rates do not fall.
Another case is software services sold to small businesses. CAC here is often much higher because there is a consulting sales team and the closing cycle takes several weeks. If CAC is 6 million VND and the subscription package is 800,000 VND per month with a 70% margin, each month the customer returns 560,000 VND, meaning it takes nearly 11 months to break even. That number is acceptable if customers stay for 2–3 years on average, but it becomes a cash-flow disaster if most customers leave after one year.
The common thread in both examples: CAC in the Vietnamese market can fluctuate sharply by season. Q4 and major sale events such as 11/11 and 12/12 push ad prices up, so a rising CAC is normal. Comparing CAC in November with CAC in March and concluding that the marketing team is underperforming is an unfair comparison.
Common Mistakes When Optimizing CAC
Most CAC problems are not about the metric being bad, but about calculating it incorrectly and then making decisions based on the wrong number.
- Counting only ad spend: leaving out salaries, agency fees, and tool fees makes CAC look 30–50% lower than reality, leading to budget increases in the wrong place.
- Mixing existing customers with new ones: the denominator swells, CAC is artificially lowered, and you can no longer see which channel is actually bringing in new people.
- Cutting budgets as soon as CAC rises: many spikes are only due to seasonality or because a new ad has not finished its learning phase. Cutting too quickly kills momentum.
- Comparing CAC with companies in other industries: the CAC of a clothing shop and the CAC of a software company are not on the same scale. Compare yourself with your own past performance.
- Chasing the lowest CAC at all costs: cheap customers are often low-quality customers who buy once and disappear. Low CAC with even lower LTV is still a loss.
- Looking only at average CAC: the overall number hides the fact that one channel is performing very well while another is burning cash. You need channel-level CAC to know what to cut.
The safest approach is to track CAC monthly together with LTV, conversion rate, and repeat purchase rate. Read together, these four metrics give the right picture; read separately, any one of them can easily be misleading.
Frequently Asked Questions About CAC
Read more: Marketing Analytics: A-Z Guide to Measuring Performance
What is a good CAC?
There is no universal benchmark for every industry. Instead of asking what CAC is good, ask what the LTV/CAC ratio is: 3 or higher is usually considered healthy, while below 1 means the more you sell, the more you lose. Also compare this month’s CAC with your own last month’s CAC, not with businesses in other industries.
How is CAC different from CPA and ROAS?
CPA is the cost of any action, which could be as simple as filling out a form or adding to cart. CAC is narrower and stricter: it only counts when a real customer buys, and it includes costs beyond advertising. ROAS, on the other hand, measures the revenue generated for every dollar spent on ads, looking only at ad spend and not salaries or tools.
Should staff salaries be included in CAC?
Yes. Marketing and sales salaries are direct costs of acquiring new customers, so they must be included in the numerator. If one person handles both new and existing customers, split their salary according to the share of time spent on acquisition. Leaving salaries out entirely gives you a number that looks nice but is useless for profit-and-loss analysis.
How can CAC be reduced without lowering sales?
The cheapest path is to improve conversion on the traffic you already have: fix landing pages, shorten checkout steps, and reply to messages faster. At the same time, gradually increase the share of unpaid channels such as SEO, email, and referrals to reduce dependence on ad prices. Cutting budgets is the fastest method, but it also easily drags sales down.
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Frequently Asked Questions
What is CAC and why does it matter to a business?
CAC (Customer Acquisition Cost) is the cost of acquiring customers, calculated by dividing total marketing and sales costs by the number of new customers in the same period. It matters because it shows how much you are paying for one customer, which tells you whether growth is profitable or just burning cash.
How do you calculate CAC and what costs should be included?
CAC equals total costs divided by the number of first-time buyers. Costs include ad budgets, marketing and sales salaries, agency or freelancer fees, tool fees, and content production costs. Leaving out salaries and tool fees is a common mistake that makes CAC look lower than it really is.
How are CAC and LTV related?
CAC is the money spent to acquire one customer, while LTV is the money that customer brings in over the time they stay with you. An LTV-to-CAC ratio of 3 or higher is usually considered healthy, while below 1 means every new customer is a loss. That is why the two metrics should be read together rather than looking at CAC alone.
