How to calculate CAC
The basic formula is simple, but the inputs are not. Total acquisition spend should include everything you spent to acquire customers in a period: paid ads, content production, agency fees, sales team salaries, software for marketing automation, sponsorships, and affiliate payouts. Divide that by the number of customers who joined during the same period.
CAC = (Paid ads + Content + Sales salaries + Tools) ÷ New customers in the period
If you spent $20,000 in March and signed up 200 new subscribers, your March CAC is $100. Whether that is good depends entirely on what those subscribers are worth over their lifetime.
Why CAC matters for subscription businesses
For a one-time-purchase store, CAC matters but is bounded — if a customer's first order doesn't cover CAC, the math is bad. For a subscription business, the calculus is different. You can spend more than the first order is worth, as long as the customer stays long enough for the cumulative revenue to clear CAC plus margin.
This is why the LTV-to-CAC ratio is the single most important health metric for subscription businesses. A common benchmark:
- LTV:CAC ≥ 3:1 — healthy, sustainable growth.
- LTV:CAC ≈ 1:1 — you are burning marketing budget for nothing.
- LTV:CAC ≥ 5:1 — you might be under-investing in growth.
Common mistakes when calculating CAC
- Including organic customers in the denominator. If a customer found you through a friend's referral, they did not cost you acquisition spend — including them deflates CAC artificially.
- Excluding tools and salaries. CAC is fully loaded spend, not just ad budget. A two-person growth team costs $200K+/year before any ads run.
- Mixing time periods. The spend in March acquires customers in March and April. For long sales cycles, attribute spend across the actual conversion window.
- Forgetting blended vs paid CAC. Track both: blended CAC (all marketing spend ÷ all new customers) tells you efficiency overall; paid CAC (paid spend ÷ paid-attributable customers) tells you the truth about your paid channels.
How to reduce CAC
Three levers, in order of leverage: improve conversion rate on the pages your traffic already lands on (better widget, clearer pricing, social proof); increase organic acquisition through SEO, referral, and content (which pulls down blended CAC over time); and narrow paid targeting to higher-intent audiences so you stop paying to acquire customers who churn quickly.