TL;DR
- Count only first-time paying customers in the CAC denominator; including returning buyers makes CAC look lower than it is.
- CPL divides by leads and CPA by ad-platform conversions, while CAC divides all acquisition costs by new paying customers.
- Repeat-purchase LTV = order value x purchases per year x years x gross margin; subscription LTV = monthly revenue x margin / churn.
- Payback months = CAC / monthly gross profit per customer; in the illustrative example, 800 / 160 = 5 months.
CAC, or customer acquisition cost, is the average amount a business spends to win one new customer. You calculate it by dividing all customer acquisition costs in a period by the number of new customers gained in that same period.
The number tells you what price your marketing and sales are paying to "buy" each customer. Compare it with LTV, the value one customer generates over the whole time they keep buying, and you know whether acquiring customers pays off. This guide covers the CAC formula with illustrative examples, how it differs from CPA and CPL, which costs to include, LTV and the LTV:CAC ratio, payback period, and practical ways to lower CAC.
What CAC is and how to calculate it
The basic formula is:
CAC = total acquisition costs in a period ÷ number of new customers in the same period
"New customers" must mean people buying or paying for the first time, not every order and not every lead. If returning customers are counted in, CAC looks lower than it really is, because those customers were not produced by this period's acquisition spend.
Illustrative example: monthly CAC
The figures below are an illustrative example to show the calculation. Suppose an online skincare shop has these costs in one month: 120,000 baht on Google and Meta ads, 20,000 baht on content and creative production, 10,000 baht on marketing tools, and 50,000 baht of marketing team salaries spent on winning new customers. The total is 200,000 baht, and the shop gains 250 new customers that month.
CAC = 200,000 ÷ 250 = 800 baht per new customer
If you count only ad spend and the customers your tracking attributes to ads, say 120,000 baht and 160 ad-driven new customers, you get a paid CAC of 750 baht. Both numbers are useful in different ways. The first, blended CAC, shows the business as a whole; the second helps decide budget for each ad channel. What matters is saying which one you mean and using the same definition every month.
How CAC differs from CPA and CPL
These three metrics are often used interchangeably even though they measure different things. The difference lies in the numerator (which costs are counted) and the denominator (which event you divide by).
| Metric | Costs counted | Divided by |
|---|---|---|
| CPL (cost per lead) | Ad or campaign spend used to generate leads | Number of leads, such as form fills or chats, who have not bought yet |
| CPA (cost per acquisition/action) | Ad spend for that campaign or platform | Conversions as defined in the ad platform, which may be a purchase, a sign-up or a call |
| CAC (customer acquisition cost) | All marketing and sales costs used to win new customers | Number of new customers who actually paid |
The distinction changes decisions. A campaign can have a very low CPL while most of its leads never buy, which makes CAC high. A CPA inside an ad platform can also look good because a conversion may be counted more than once, or the platform counts existing customers who clicked an ad and bought again. CAC is the closest to real money, but the slowest to calculate because it pulls data from several systems. Most teams use CPL and CPA to adjust campaigns day to day, then check CAC monthly or quarterly to see whether those adjustments lowered the real cost per customer.
Illustrative example: a training course business spends 60,000 baht and gets 300 leads (CPL of 200 baht). The sales team closes 30 of them, so CAC based on ad spend alone is 2,000 baht. Add 30,000 baht of sales salaries and commission, and full CAC becomes 3,000 baht. The 200 baht shown in the ad report is 15 times lower than the real cost per customer.
Which costs to include in CAC
There is no mandatory standard, but the more completely you count, the more useful the number becomes for decisions. Items to consider:
- Ad spend across every channel, such as Google Ads, Meta, TikTok, LINE and marketplace ads
- Production of creative, video, images and content used to win new customers
- Agency, freelancer and influencer fees
- Software such as CRM, analytics tools and chat systems, in proportion to their use for acquisition
- Salaries and commission for marketing and sales staff, in proportion to time spent on new customers
- Discounts or gifts given only to first-time customers. Some teams count these in CAC, others deduct them from revenue; pick one and use it consistently
Do not include cost of goods, shipping, or the cost of looking after existing customers such as an after-sales team. Those belong in profit and LTV calculations instead.
The timing problem
For businesses with long sales cycles, such as B2B or real estate, money spent this month may produce customers three months later. Dividing this month's costs by this month's customers makes the number swing wildly. The fix is to use a multi-month average, for example the last three months of costs and new customers combined, or to shift the cost window to match the average sales cycle.
What LTV (CLV) is and the LTV:CAC ratio
LTV (lifetime value), also called CLV (customer lifetime value), is the value one customer generates for the business over the whole period they remain a customer. To compare it fairly with CAC, base LTV on gross profit rather than revenue, because CAC has to be paid back out of profit.
LTV formula for repeat-purchase businesses
LTV = average order value × purchases per year × years as a customer × gross margin
Illustrative example, continuing the skincare shop: average order value 1,200 baht, 4 purchases a year, an average customer life of 2 years, and a 40 percent gross margin. LTV = 1,200 × 4 × 2 × 0.40 = 3,840 baht.
LTV formula for monthly subscriptions
LTV = average monthly revenue per customer × gross margin ÷ monthly churn rate
Illustrative example: a 500 baht monthly plan, 70 percent gross margin, and 5 percent of customers cancelling each month. LTV = 500 × 0.70 ÷ 0.05 = 7,000 baht.
How to read the LTV:CAC ratio
In the skincare example, LTV of 3,840 baht divided by CAC of 800 baht gives a ratio of about 4.8 to 1, meaning one customer produces almost five times the gross profit it cost to acquire them. A ratio below 1 to 1 means the business loses money on every new customer. Many teams use 3 to 1 as a rough reference point, but it is a rule of thumb, not an industry-wide standard; each business's fixed costs and how fast money comes back matter more. A very high ratio is not always good either. It can mean the business is underinvesting in acquisition and leaving customers to competitors.
One caution: LTV is a forecast. A business only a few months old has no data on how long customers stay. Assume too many years and LTV looks better than it is, which encourages overspending. Start with conservative assumptions and adjust once you have real repeat-purchase data.
CAC payback period: how many months to earn it back
The LTV:CAC ratio tells you whether acquisition pays off, but not when. CAC payback period answers that.
Payback period (months) = CAC ÷ gross profit per customer per month
Illustrative example: the skincare customer spends 1,200 × 4 = 4,800 baht a year, or 400 baht a month. At a 40 percent gross margin that is 160 baht a month. Payback = 800 ÷ 160 = 5 months. The business needs enough cash to wait five months before each customer starts generating profit, and the faster it grows, the more cash it needs up front. That is why a business with a healthy LTV:CAC can still run short of cash if the payback period is longer than its cash reserves allow.
How to lower CAC with SEO, remarketing and CRM
There are two ways to lower CAC: spend less to acquire customers, or win more new customers for the same spend. The approaches that work over the long run usually do both.
SEO: traffic without a per-click cost
SEO has high upfront costs for site work and content, but once pages rank, customers who arrive from search do not cost a click each time. Spread SEO costs over customers won across many months and the CAC of this channel tends to fall over time. Ads are different: when you stop paying, the customers stop too. See the SEO service for an approach.
Remarketing: win back people who nearly bought
Most visitors do not buy on their first visit. Remarketing shows ads to people who have visited the site, viewed a product or added something to the cart. They already know the brand, so they often convert at a lower cost per person than entirely new audiences. Make sure to exclude people who have already bought, or you will pay to reach existing customers and the platform will count conversions that did not add a new customer. See the remarketing service.
CRM and LINE OA: raise LTV and win referrals
CRM does not lower CAC directly, but it improves the LTV:CAC ratio because customers buy more often and stay longer. A refer-a-friend program run through your existing customer base is also a way to win new customers at a typically low cost per person, since you pay only when someone signs up or buys. In Thailand, LINE OA is a channel customers already use, and, combined with a CRM, it can be used to segment customers by behaviour, time messages to purchase cycles and tag where each customer came from. See the scope of the LINE CRM service.
Improve conversion rate
If a landing page lifts its visitor-to-customer rate from 1 percent to 1.5 percent on the same ad budget, new customers increase by half and CAC falls by about a third (illustrative example). Making the page load faster, answering the concerns customers have and cutting form steps often lowers CAC without touching the ad budget at all.
Point ads at people ready to buy
In Google Ads, keywords with clear purchase intent, such as those containing price, buy or a model name, usually bring customers at a lower cost than broad terms. Adding negative keywords to cut irrelevant searches, and sending real sales data back into the platform so automated bidding learns from actual customers instead of all leads, keeps budget on people likely to buy. See the Google Ads service. For lead-based businesses, a system that qualifies leads before passing them to sales also cuts the time sales staff waste on leads that will never buy; see the lead generation service.
Common mistakes when calculating CAC
- Counting only ad spend and calling it CAC, then scaling budget even though the real cost is much higher.
- Counting returning customers together with new ones, which makes the number too low.
- Comparing CAC with first-order revenue instead of lifetime profit.
- Changing the cost definition every month, so trends cannot be read.
- Using ad platform conversions as the new-customer count, even though platforms may double count across channels.
CAC in the Thai market: what makes it hard to measure
Many Thai businesses close sales in chat, through LINE, Facebook Messenger and marketplace chat. A customer sees an ad, sends a message and transfers money without passing through a website checkout. The ad platform never sees that sale, so CAC calculated from ad platform data can be too high or too low. A workable fix is to tag each customer's source from the first message, for example using a campaign-specific link or a pre-filled first message unique to each campaign, then record sales in a CRM so you can count real new customers at month end.
Multi-channel selling is the other issue. A customer sees a Facebook ad but buys on Shopee. If you calculate CAC per channel, the Facebook ad looks expensive even though it drove sales somewhere else. Business-level blended CAC is the number to use for big decisions, while per-channel CAC is better for directional comparisons.
FAQ about CAC
What is CAC and how is it calculated?
CAC is the average cost of winning one new customer, calculated by dividing all marketing and sales costs spent on acquiring new customers in a period by the number of new paying customers in the same period.
What is the difference between CAC and CPA?
CPA is usually ad spend divided by conversions as defined in the ad platform, while CAC includes all acquisition costs and divides by new customers who actually paid. CAC is therefore usually higher and closer to the real cost.
What is a good LTV:CAC ratio?
No single number fits every business. A ratio below 1 to 1 means acquisition loses money; many teams use 3 to 1 as a rough reference, but you should read it together with payback period and the cash the business has.
What is CLV, and is it different from LTV?
CLV (customer lifetime value) and LTV (lifetime value) are the same idea: the value one customer generates for the business over the whole time they remain a customer. Base it on gross profit so it compares fairly with CAC.
If you do not yet know your CAC, start by adding up last month's acquisition costs and counting real new customers using the formula in this guide, then see which channel to fix first. The Relevant Audience team can help set up campaigns measured all the way to real customers; see the Google Ads service.
