Customer Acquisition Cost: How to Calculate It Accurately and Reduce It Systematically

The correct CAC formula#

The most common CAC calculation mistake is including only media spend. Correct CAC = Total Sales and Marketing Spend / Number of New Customers Acquired. Total spend includes: all advertising (paid search, paid social, display, email platforms, SEO tools), sales team salary and commissions fully loaded, marketing team salary fully loaded, agency and contractor fees, event and trade show costs, and marketing technology. If you spent £20,000 on sales and marketing in a month and acquired 200 new customers, your CAC is £100 — regardless of how much of that £20,000 was media spend.

CAC by channel: the analysis that changes strategy#

Blended CAC hides dramatic variation between channels. Paid search CAC might be £45. Paid social £85. Organic content £12. Email £8. Referrals £25. Each channel has a different CAC and a different quality of customer expressed in LTV. The strategy-defining analysis is not which channel has the lowest CAC, but which channel has the best LTV:CAC ratio. A channel with £85 CAC but customers who generate £850 LTV is better than a channel with £45 CAC where customers generate only £150 LTV.

CAC payback period#

CAC payback period = CAC / Monthly Gross Profit Per Customer. If CAC is £120 and a customer generates £25 gross profit per month, payback is 4.8 months. This metric tells you how long your business is cash-flow-negative on each new customer. A payback period above 12 months requires external capital to fund growth. A payback period below 6 months is excellent and allows faster reinvestment into additional acquisition.

Five levers to reduce CAC#

Shift spend toward lower-CAC channels. Improve conversion rates — the same media spend with higher conversion produces lower CAC. Build organic channels — SEO, content, and referral programmes produce customers at near-zero variable cost once established. Improve offer quality — a more compelling offer converts better, reducing the spend required per acquired customer. Reduce churn — when customers stay longer, word-of-mouth referrals increase and organic acquisition rises, reducing paid CAC over time.

Tracking CAC with AskBiz#

AskBiz calculates CAC from your connected marketing spend data and customer acquisition records. It tracks CAC by channel, calculates CAC payback period, and monitors the LTV:CAC ratio as continuous time-series metrics. Ask it: what is my blended CAC this month vs last quarter, which channel has the best LTV:CAC ratio, how has my payback period changed since I increased paid social spend.