What is CAC in fashion e-commerce?
Customer acquisition cost: the total marketing and sales spend required to win one new customer.
In short
CAC, or customer acquisition cost, is the average amount a fashion brand spends on marketing and sales to gain one new customer. It is calculated by dividing acquisition spend over a period by the number of new customers won in that period, and it is a key measure of growth efficiency.
How does it work in practice?
A brand adds up the costs of acquiring customers, such as paid search and social ads, influencer fees, affiliate commissions, first-order discounts and sometimes agency and creative costs. It divides the total by the number of first-time buyers. CAC can be calculated as a blended figure for the whole business or by channel, campaign, country or customer segment, which requires an attribution model to assign customers to the right source.
The number is most useful when set against the value a customer brings over time. If a customer costs more to acquire than the gross margin they generate across their purchases, growth destroys value.
Why does it matter for fashion businesses?
Many fashion brands grew rapidly through paid social advertising, only to find that acquisition costs rose as competition for ad space increased and tracking became harder. Monitoring CAC by channel helps brands shift budgets to efficient sources, invest in retention and community, and decide how far to rely on own retail, wholesale or marketplaces for customer reach.
How is AI changing it?
Ad platforms increasingly use AI to automate bidding and targeting, which can lower CAC but also makes results harder to interpret. Brands use propensity and lifetime value models to target prospects who are likely to become valuable customers, not just cheap first-time buyers.
Common pitfalls
- Excluding discounts, returns or creative costs, which makes CAC look lower than it is.
- Optimising for low CAC while acquiring customers who never buy again.
- Relying on platform-reported figures without independent measurement.
Frequently asked questions
How do you calculate customer acquisition cost?
Divide the total cost of acquiring customers in a period, including marketing spend and related costs, by the number of new customers acquired in that period. It can be calculated overall or by channel.
What is a good CAC to CLV ratio?
There is no universal benchmark, but the lifetime value of a customer should comfortably exceed their acquisition cost on a margin basis. The right ratio depends on the brand's margins, cash position and growth strategy.