What is customer acquisition cost (CAC)?

Written by Madalena Rugeroni, founder of Mazo · Updated 15 September 2026

Customer acquisition cost (CAC) is the average cost of winning one new paying customer: total sales and marketing spend in a period divided by the number of new customers acquired in that period. A fully loaded CAC includes salaries, commissions, tools, agencies and content, not just advertising spend.

CAC formula

CAC = total sales and marketing costs in a period ÷ new paying customers in that period

Blended CAC uses all spend and all new customers. Channel CAC assigns spend and customers to each channel — outbound, paid ads, content — and is what you actually make decisions with. Divide by paying customers, never by signups or trials.

Worked example

A fictional B2B SaaS spends €24,000 on sales and marketing in a quarter and wins 20 new customers.

Blended CAC: €24,000 ÷ 20 = €1,200.
Outbound: a salesperson (€12,000 for the quarter) plus tools (€2,000) won 12 customers: €1,167 each.
Paid ads: €6,000 won 4 customers: €1,500 each.
Content: a freelance writer (€4,000) won 4 customers: €1,000 each.

Ads-only accounting would have reported a CAC of €300 (€6,000 ÷ 20) — four times too low.

Why CAC matters from €0 to €1M ARR

Pre-revenue to 10 customers: your CAC is mostly founder time. Don't compute a number; note which conversations turned into customers.
Around €10k MRR: start tracking CAC by channel. Keep a note of founder hours, so a founder-powered channel isn't mistaken for a cheap one you could hand off.
€50k+ MRR: knowing CAC by channel is one of the first things a Series A investor checks — and it only means something next to CAC payback.

Mazo's rule of thumb: calculate CAC by channel and fully loaded, then judge it by how fast it pays back rather than on its own: before €1M ARR, aim for a CAC payback under 12 months; under 6 is excellent.

Common CAC mistakes

Counting ad spend only. Salaries and tools are usually the biggest part of B2B CAC.
Dividing by signups. Trials that never pay aren't customers.
Mismatched timing. With a 60-day sales cycle, this quarter's spend wins next quarter's customers.
Pouring more leads into a leaky funnel. It raises CAC, not revenue — fix conversion first.
Buying more search ads when CAC climbs. Chris Walker's diagnosis: rising paid CAC with flat volume means the existing demand pool is drained, and the fix is creating demand, not more budget.

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FAQ

What is a good CAC for B2B SaaS?

There is no good CAC in isolation, because it depends on what a customer pays. Judge CAC by payback: how many months of gross-margin-adjusted revenue it takes to earn it back.

Should CAC include salaries?

Yes. Fully loaded CAC includes the share of salaries, commissions, tools, agencies and content spent on acquiring customers. Excluding them makes most B2B channels look far cheaper than they are.

What is the difference between CAC and cost per lead?

Cost per lead divides spend by leads generated. CAC divides spend by new paying customers, so it captures how well those leads convert.

Who wrote this

Madalena Rugeroni built Mazo. She's an ex-Googler, a startup advisor and investor, and runs a portfolio of internet companies. Before that, as Head of Growth at Amplemarket, she scaled a B2B SaaS to $10M ARR. LinkedIn

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Further reading. Operators and books referenced: Chris Walker (demand creation vs capture). These are published methodologies credited to their authors; Mazo is not affiliated with or endorsed by them.