Customer acquisition cost (CAC) is how much it costs you, on average, to acquire one new paying customer. It is one of the two numbers that define whether a business is unit-economics positive, the other being LTV.
The Basic Formula
CAC = Total sales and marketing spend ÷ New customers acquired
Both figures should cover the same time period, typically a month or quarter.
Example: if you spend $20,000 on sales and marketing in a quarter and acquire 100 new customers:
CAC = $20,000 ÷ 100 = $200 per customer
What to Include in Sales and Marketing Spend
This is where CAC calculations differ between companies. A fully-loaded CAC includes:
- Paid advertising (Google, Meta, LinkedIn, etc.)
- Salaries and commissions for sales and marketing staff
- Agency and contractor fees
- Software tools (CRM, email platform, ad analytics)
- Content production costs
- Trade shows and events
- Free trial and freemium infrastructure costs
A narrower "paid CAC" includes only direct ad spend. Both are useful, but you should be clear about which one you are quoting.
Blended CAC vs. Channel CAC
Blended CAC averages across all acquisition channels. This is useful for overall unit economics but hides which channels are efficient.
Channel-level CAC tells you where to invest more:
- Paid search CAC: $180
- Organic/SEO CAC: $40 (counting content production costs)
- Referral program CAC: $60
- Trade show CAC: $420
Channels with low CAC and high customer quality (good retention, high ARPU) should receive more budget. Channels with high CAC or low-quality customers should be reduced or cut.
The LTV:CAC Ratio
CAC becomes meaningful when compared to LTV:
LTV:CAC = Customer lifetime value ÷ CAC
A ratio of 3:1 is the commonly cited benchmark for healthy SaaS businesses: for every dollar spent acquiring a customer, you earn three dollars in gross margin over their lifetime.
At 1:1, you break even on acquisition and need to find margin elsewhere. Below 1:1, you are destroying value with every customer acquired.
CAC Payback Period
A practical companion metric to LTV:CAC is the payback period, which tells you how long it takes to recover your acquisition cost:
Payback period (months) = CAC ÷ Monthly gross profit per customer
If your CAC is $200 and each customer generates $25 in gross profit per month:
$200 ÷ $25 = 8 months payback
A shorter payback period means growth requires less working capital. Consumer SaaS often targets 12 months or under; enterprise SaaS may accept 24+ months with contract commitments.
Why CAC Increases Over Time
For most companies, the earliest customers are the easiest to acquire (existing demand, lowest competition, word of mouth). As you grow, you exhaust your best channels and must pay more per customer. This is why LTV needs to grow alongside CAC, through price increases, upsells, or reduced churn, rather than staying constant while CAC climbs.
Tracking CAC by cohort (customers acquired each quarter) helps identify this trend early.