In marketing, CAC means customer acquisition cost: what you spend on average to win one new customer. You take your acquisition spend for a period and divide it by the number of new customers in that same period. CAC tells you the price of each new face that walks into your business, ads and sales effort included. It helps you check that your growth is profitable, split your budget between channels, and set a ceiling for your bids. This guide is for businesses that buy traffic on Google Ads or Meta Ads and want to connect that spend to real customers, in ecommerce, lead generation or subscriptions.

What CAC Is Used For

CAC answers a simple question: does a new customer cost you less than what they leave you? It guides three decisions:

  • Check that your growth is profitable: read CAC against the customer's margin. Against the margin of the first order, it tells you if the sale pays for itself right away. Against margin LTV, it tells you if the customer pays for themselves over time.
  • Split your budget between channels: Google Ads, Meta Ads, trade shows, outbound sales. Each channel has its own CAC, and the budget goes where a customer costs the least for the value they bring.
  • Set a ceiling for your bids: a maximum CAC translates into a target CPA or a target ROAS, so the campaign knows how high it can go.

My recommendation is to set, from the start, the acquisition cost your margin can carry, product by product, and to let that number decide the budgets.

How To Calculate CAC

The basic formula:

CAC = acquisition spend for the period ÷ new customers in the period

Everything depends on what you count as acquisition spend. Two versions exist side by side:

  • Ad CAC: media spend only. This is the Google Ads version. According to Google Ads Help, Customer Acquisition Cost is the ad spend allocated to new customers, divided by the total of unique new customers acquired through a campaign.
  • Full CAC: media spend, plus everything that turns a prospect into a customer. Sales time, tools, service providers, welcome discounts.

Here is an example calculation: 6,000 EUR of advertising and 2,000 EUR of sales costs in one month, for 100 new customers. Full CAC is (6,000 + 2,000) ÷ 100 = 80 EUR. The CAC calculator runs this calculation and compares it with your ad cost per conversion.

CAC Or CPA: Two Numbers For Two Questions

CPA counts trips to the checkout. CAC counts new faces. CPA divides your spend by all conversions: first orders, repeat orders, and sometimes actions that come before the purchase. CAC only divides by customers who buy from you for the first time.

The two numbers split as soon as your customers come back. Google says so in its help: when your conversion count is set to "every", each repeat purchase by a new customer counts as one more conversion, while the "New Customers" column counts each customer once. In the same month, your CPA can show 20 EUR and your CAC 60 EUR. CPA runs a campaign day to day. CAC tells you what your growth is worth.

Six customers on a timeline: each one enters with a first order, then may come back. On the right, the white stack counts every conversion, the gradient stack counts only new customers

What Google Ads Counts On A Real Store

I measure it on an online store I work with. Over the 90 days before October 15, 2026, its Shopping and Search campaigns cost 10,192 EUR for 546 sales, which is 18.66 EUR per sale. The "New vs. returning customers" segment sorts these sales like this:

  • 91 sales from new customers;
  • 18 sales from returning customers;
  • 437 unknown sales, which Google could not classify.

So the ad CAC of this store sits between two limits. If every unknown sale comes from a new customer, CAC drops to 19.29 EUR. If only the 91 recognized new customers count, CAC rises to 112 EUR, which is 5.8 times higher. Only the store's order database can decide between the two.

Google explains these unknown sales in its help page on lifecycle goals. They are conversions it cannot identify as new or existing because of measurement limits on iOS or user personalization settings, plus conversions linked to sensitive categories. To shrink this grey zone, the same page recommends the new vs. existing customer parameter in your conversion tracking tag. It gives Google the ground truth, customer by customer. An up-to-date customer list also helps it recognize your existing customers.

Where To Find CAC In Google Ads

Google Ads shows a CAC under one condition: the "Customer acquisition" lifecycle goal is active on the campaign, and the campaign optimizes for Purchase conversions. You then find, in the campaigns table:

  • the New Customers column, which counts the campaign's unique new customers;
  • the Customer Acquisition Cost (CAC) column, not available for Demand Gen at this time;
  • the New vs. returning customers segment, which splits your conversions into new, returning and unknown customers.

This data starts on the day you activate the goal. Google states that it is not available retroactively. It also notes that CAC is usually higher for new customers: they cost more to acquire, and they bring higher long-term value.

Common Mistakes

  • Dividing by the Conversions column: you get a cost per conversion, repeat orders and micro-actions included. It is not a CAC: presented as one, it makes your growth look cheaper than it is.
  • Forgetting non-media costs: an ad CAC of 40 EUR can become a full CAC of 90 EUR once sales time is counted. Both are useful, as long as you say which one you give.
  • Shifting periods: with a three-month sales cycle, March customers often come from December ads. Match spend and customers on the same group, or use a longer period.
  • Judging a CAC on its own: 150 EUR is an excellent CAC for a customer who leaves 1,200 EUR of margin, and too high for a customer who leaves 60. The number only makes sense next to the margin.

The Limits Of CAC

CAC is an average for a period. It mixes the customer won through a search for your brand with the one won after six clicks on three channels. Calculated by channel, it depends on the attribution model that shares credit between those channels, and two tools can give two different CACs for the same campaign.

It also tells you what a customer cost, without telling you what they are worth. A rising CAC can be good news if the new customers are better. That is why you always read it with LTV, and with the time it takes to pay it back.

The Three Most Searched Questions

What is a good CAC? A CAC your margin pays back. First, compare it with the margin of the first order: below that, each sale pays for itself. Then compare it with margin LTV. The CLV:CAC ratio guide explains the benchmarks that show if your growth creates value.

How do you calculate the CAC payback period? Divide your CAC by the monthly margin of one customer, which is their monthly revenue multiplied by your gross margin rate. A CAC of 200 EUR against a 29 EUR monthly plan at an 80% margin pays back in 8.6 months. The CAC payback period calculator does this for you.

What is the average customer acquisition cost in ecommerce? The number that matters is yours, because it depends on your order value, your margin and how loyal your customers are. A store with a 60 EUR average order and a store with a 600 EUR average order live with very different CACs. Calculate your ceiling from your margin before you look at a market average.

To start, run the numbers on your last quarter: ad spend on one side, first orders from your database on the other. If the gap with the Google Ads cost per conversion surprises you, you have the starting point for a Google Ads audit, and for a growth marketing engagement that connects your campaigns to your real customers.