Glossary
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customer-acquisition-cost-cac
CAC (customer acquisition cost): formula, calculation by channel, CLV and ROAS comparison, Shopify measurement, and key profitability metrics.
Updated on
June 4, 2026
The CAC (Customer Acquisition Cost) measures how much it costs, on average, to acquire a new customer over a given period. Standard formula: marketing and sales expenses ÷ number of new customers. It is a key KPI to judge whether your customer acquisition is profitable in relation to your margin and 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, 12-month window without purchase, or converted email. Without a unique definition, the CAC will vary between teams.
Why CAC is a key metric in e-commerce
Scaling ads without tracking CAC means 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 the CAC is skyrocketing (iOS tracking, seasonality); Pricing: a high CAC requires sufficient margin or AOV (AOV); Investors: 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 > 3 ratio in 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 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); Creative: shooting, paid UGC (according to accounting method).
Often excluded: COGS, logistics, product/customer service salaries (except pure B2B acquisition sales team).
In practice, Shopify beauty 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 customers = 13,500 ÷ 270 = €50. Average gross margin on first purchase: €38 → acquisition not profitable 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 → Meta CAC = €44.44. Allows budget reallocation.
Track CAC with Shopify and marketing tools
Shopify does not always display a single native "CAC"; build it by combining sources:
In Shopify, this translates specifically to: 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).
Points of attention in Shopify:
In Shopify, this translates specifically to: Tagging UTMs on all campaigns; Using the same attribution window as your ad platforms (7 d vs 1 d); Exporting new customers per month from Reports > Customers; Crossing 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 for driving profitable acquisition
Points of vigilance include: Calculate monthly and by channel, not just once a year; Include hidden costs (agency, creatives, promo codes for acquisition); Compare CAC to the margin of the first purchase, not just to revenue; Optimize conversion before increasing budget (CAC decreases if spend is the same but with more customers); Invest in retention to improve CLV/CAC without lowering CAC; Segment: CAC for new customers in France vs. export.
Watch out for:
Points of vigilance include: Dividing ad spend by all orders (underestimates CAC); Ignoring organic customers (blended CAC decreases artificially if poorly counted); Confusing 4× ROAS with profitable CAC (low margin = trap); Comparing January CAC (sales period) and August CAC without context; Not updating after a tracking or pixel change; Scaling a campaign where CAC > gross margin without a repeat plan.
In brief
Takeaway: CAC = marketing/sales cost ÷ new customers; central KPI for acquisition profitability; must 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.
Associated terms, FAQ, and useful resources
Associated terms
Customer Acquisition: the strategy behind CAC.
CLV: complementary metric (CLV / CAC).
LTV: common synonym for CLV.
ROAS: ad spend return, not cost per customer.
FAQ
What is a "good" CAC in e-commerce?
There is no universal number. A CAC is good if it is lower than the margin and the CLV that this customer generates. Compare it to your industry, product margin, and repeat purchase rate.
CAC and CPA: what is the difference?
CAC targets the new customer. CPA in ads usually refers to the cost per conversion (purchase), including recurring customers. Clarify the metric in your reports.
Should SEO be included in the 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 conversion rate, target ads better, test creatives, increase AOV, develop SEO/email ("free" media customers), and build loyalty to amortize CAC over multiple purchases.
Go further
Sources: focus points for DTC metrics, Shopify Analytics client reports. CLV/CAC ratios: adapt to your cash flow and your accountant.
Enzo
June 4, 2026
