What is CAC (Customer Acquisition Cost)? — Definition for DTC operators

Definition

CAC is the total cost to acquire a new customer, calculated as marketing spend divided by new customers acquired in the same window. Paid CAC counts only ad spend over new customers from ads; fully-loaded CAC includes agency fees, creative production, and influencer payments.

How operators actually use it

Operators monitor CAC against their LTV-to-CAC ratio — a 3:1 ratio is the rule-of-thumb floor for a healthy DTC business, with payback inside 6-12 months. Rising CAC is the leading indicator that creative is fatiguing, audiences are saturating, or competitors have entered your bid space. CAC is the most useful single number to share with investors because it is hard to fake.

Common pitfalls and honest-cost notes

The most common CAC mistake is dividing by all new orders instead of all new customers — if 30% of new buyers already shopped your brand on a different email, your 'new customer' count is inflated and CAC is understated. Use customer-level deduplication (or `customers.shopify`) and compare apples to apples month over month.

Related terms

Blended CAC — Blended CAC is total marketing spend divided by total new customers, regardless of whether each customer was attributed to a paid source.
LTV (Lifetime Value) — LTV is the projected total revenue a customer will generate over their relationship with your brand.
Payback Period — Payback period is the number of days or months it takes for the contribution margin from a customer cohort to fully cover the CAC spent to acquire that cohort.
Cohort Analysis — Cohort analysis groups customers by a shared attribute (usually first-order month) and tracks how that group behaves over time — revenue, retention, repeat rate, refund rate.
ROAS (Return on Ad Spend) — ROAS is revenue divided by ad spend, usually reported per platform (Meta ROAS, Google ROAS) and as a blended figure across all paid channels.