What Is Customer Acquisition Cost (CAC) in SaaS?
CAC measures the total cost of acquiring one new paying customer, and is the foundation of every SaaS unit economics calculation.
Key Takeaways
- CAC = total sales and marketing spend / number of new customers acquired
- Always match the time period: spend in Q1 divided by customers acquired in Q1
- Blended CAC hides channel efficiency — track CAC by channel where possible
- CAC is only meaningful alongside LTV and payback period
The CAC formula
Customer Acquisition Cost = total sales and marketing costs in a period divided by number of new customers acquired in that period. Costs should include salaries for sales and marketing staff, advertising spend, software tools used for acquisition, and a proportional share of leadership time spent on sales. The most common mistake is under-counting cost — founders often exclude their own time, which can dramatically understate true CAC for early-stage businesses where founders are the primary sales motion.
Blended vs channel CAC
Blended CAC averages across all acquisition channels. It is useful for overall unit economics but hides channel efficiency. A business spending £10k/month on paid ads acquiring 5 customers and £5k on content acquiring 20 customers has very different CAC by channel. Tracking channel-level CAC allows you to double down on the most efficient channels and cut or fix underperforming ones. For SMEs with limited budget, identifying and concentrating on the lowest-CAC channel is often more valuable than broad multi-channel spending.
What a good CAC looks like
CAC in isolation means little — it must be compared to customer lifetime value (LTV). A healthy SaaS business targets an LTV:CAC ratio of at least 3:1, meaning each customer generates three times the cost to acquire them. CAC payback period (months to recoup CAC from gross margin) should ideally be under 12 months for SMB SaaS and under 18 months for mid-market. If CAC payback exceeds 24 months, the business needs significant capital to fund growth and carries material risk if churn accelerates.
Reducing CAC
The most reliable CAC reduction levers for SME SaaS are building organic acquisition channels (SEO, content, community, product-led referrals) that generate leads at near-zero marginal cost, improving sales conversion rates so the same spend acquires more customers, and shortening the sales cycle so time-based costs (salesperson hours) per deal fall. Product-led growth — where the product itself drives trial and conversion — can dramatically reduce CAC by removing the need for a sales-touch for smaller accounts.