Glossary
CAC (Customer Acquisition Cost): e-commerce definition
June 4, 2026
The CAC (Customer Acquisition Cost) measures how much it costs, on average, to acquire a new customer over a period. Standard formula: marketing and sales expenses ÷ number of new customers. It is a key KPI to judge whether your customer acquisition is profitable compared to the margin and the CLV.
Summary
Definition of Customer Acquisition Cost
The CAC answers the question: "How much did I spend to acquire one additional paying customer?"
Basic formula:
CAC = (Marketing + sales expenses over the period) ÷ (New customers over the same period)
Example: €12,000 in ad spend + agency fees over a quarter, 400 new customers → CAC = €30.
Useful distinctions:
The concept is better understood by distinguishing several elements: CAC vs customer acquisition cost: same metric; CAC is the common English acronym in e-commerce; Blended CAC vs CAC per channel: global across all sources vs Meta alone, Google alone, etc.; CAC vs CPA (Cost Per Acquisition): CPA often refers to the cost per advertising conversion (sometimes per order, not always a new customer); CAC vs ROAS: ROAS = revenue generated ÷ ad spend; CAC = cost ÷ customers (different unit); CAC vs CPC: CPC = cost per click; many clicks do not become customers.
Define internally what a new customer is: first lifetime purchase, a 12-month window with no purchases, or a converted email. Without a single definition, the CAC will vary between teams.
Why CAC is a key metric in e-commerce
Scaling ads without tracking CAC is growing in volume while losing money.
Its effects can be seen at several levels: Profitability: compare CAC to gross margin per customer and to CLV (CAC vs LTV); Budget: forecast how much to invest for X new customers; Channel mix: identify sources where CAC is skyrocketing (iOS tracking, seasonality); Pricing: a high CAC requires sufficient margin or AOV (AOV); Investors: a standard metric in DTC to evaluate growth efficiency; Promotions: acquisition discounts inflate the real CAC if not accounted for.
Rule of thumb: aim for a CLV / CAC ratio > 3 over the long term (indicative, varies by industry and cash flow). A low CAC with zero CLV (no repeat purchases) remains a dead end.
Calculation and interpretation of the acquisition cost
What to include in expenses (to be harmonized internally):
The elements to observe are as follows: Advertising: Meta, Google, TikTok, paid influencers; Agency / freelancers marketing; Tools: email, analytics, acquisition apps (variable part); Creation: shooting, paid UGC (depending on accounting method).
Often excluded: COGS, logistics, product/customer service salaries (except pure B2B acquisition sales team).
In practice, beauty Shopify store, month of March: Meta €8,000, Google €3,000, agency €2,000, tools €500 = €13,500. Shopify Analytics: 450 customers, including 270 first-time buyers (new). Blended CAC on new = 13,500 ÷ 270 = €50. Average gross margin first purchase: €38 → non-profitable acquisition at first order; estimated 12-month CLV €95 → CLV/CAC ratio = 1.9 (to be improved via repeat and email).
Calculation by channel: Meta alone €8,000 for 180 new customers → CAC Meta = €44.44. Allows budget reallocation.
Track CAC with Shopify and marketing tools
Shopify does not always display a single native "CAC"; construct it by cross-referencing sources:
In Shopify, this is particularly reflected in: Shopify Analytics: "New vs Returning" customer report, sales by channel; Meta / Google Ads: cost, conversions, cost per purchase (CPA proxy); Google Analytics 4: user acquisition, campaigns, imported cost if linked; Spreadsheet or BI: consolidated monthly CAC formula (e-commerce analytics).
Shopify focus points:
In Shopify, this is particularly reflected in: Tagging UTMs on all campaigns; Using the same attribution window as your ad platforms (7 days vs 1 day); Exporting new customers per month from Reports > Customers; Cross-referencing with gross profit by first-order cohort.
Attribution apps (Triple Whale, Northbeam, etc.) help post-iOS14, but the definition of "new customer" remains your business rule.
Key points to consider for driving profitable acquisition
Points of vigilance notably include: Calculate monthly and by channel, not just once a year; Include hidden costs (agency, creatives, acquisition promo codes); Compare CAC to margin on the first purchase, not just to revenue; Optimize conversion before increasing budget (CAC decreases with same spend, more customers); Invest in retention to improve CLV/CAC without lowering the CAC; Segment: CAC of new customers in France vs. export.
Things to watch out for:
Points of vigilance notably include: Dividing ad spend by all orders (underestimates the CAC); Ignoring organic customers (blended CAC artificially decreases if poorly counted); Confusing ROAS 4× and profitable CAC (low margin = trap); Comparing January CAC (sales) and August CAC without context; Failing to update after a tracking or pixel change; Scaling a campaign where the CAC > gross margin without a repeat plan.
In brief
Key takeaways: CAC = marketing/sales cost ÷ new customers; central KPI for acquisition profitability; to be crossed with CLV and margin; Distinct from CPA, CPC, ROAS (different units); Shopify + ads + GA4 + defined "new customer" rule; Monthly tracking by channel; optimize conversion and repeat.
Related terms, FAQ, and useful resources
Associated terms
Customer acquisition: strategy behind the CAC.
CLV: complementary metric (CLV / CAC).
LTV: common synonym for CLV.
ROAS: advertising return, not cost per customer.
FAQ
What CAC is "good" in e-commerce?
There is no universal figure. A CAC is good if it is lower than the margin and the CLV that this customer generates. Compare it to your sector, product margin, and repeat purchase delay.
CAC and CPA: difference?
The CAC targets the new customer. In ads, CPA often refers to the cost per conversion (purchase), including recurring customers. Clarify the unit in your reports.
Should SEO be included in CAC?
Organic traffic has no direct media cost, but content and SEO do have a cost (writing, tools). Many calculate a separate paid CAC and a blended CAC including content costs.
How to lower your CAC?
Improve the conversion rate, target ads better, test creatives, increase AOV, develop SEO/email ("free" customers in media), and build loyalty to amortize CAC over multiple purchases.
Go further
Sources: focus points for DTC metrics, Shopify Analytics customer reports. CLV/CAC ratios: adapt to your cash flow and your accountant.
Enzo
13 May 2026
Convert over 2,000 customers on average per month with Qstomy.
The world’s 1st Shopify AI dedicated to customer conversion
Empowering 200+ e-commerce merchants
Subscribe to the newsletter and get a personalized e-book!
No-code solution, no technical knowledge required. AI trained on your e-shop and non-intrusive.
*Unsubscribe at any time. We do not send spam.