Customer Acquisition Cost: how much you spend on average to acquire one new customer.
In practice
The basic calculation: total sales and marketing spend over a period, divided by the number of new customers acquired in that same period. The most common trap is forgetting to include sales/marketing salaries and tool costs — a CAC that only counts paid ad spend is almost always underestimated. CAC only means something next to LTV: a low CAC on a low-value product can end up costing more than a high CAC on a highly retentive one.
The formula
CAC = (sales + marketing spend over a period) ÷ (new customers won in that same period)
- Spend
Everything it cost to win those customers: ads, tools, agencies, content, and the salaries of the people doing the selling and the marketing.
- New customers
Paying customers who signed up in the period — not leads, not free sign-ups, unless free is your product.
- Period
A month or a quarter: long enough for the spend and the customers it produced to land in the same window. Sales cycles longer than that need a lag (see the FAQ).
Two useful variants: blended CAC (all channels, all customers, organic ones included) and paid CAC (paid spend ÷ customers attributed to paid). Blended flatters you; paid tells you what one more euro buys.
Worked example
A B2B SaaS over one quarter
- Ads and sponsorships: €18,000. Marketing tools and freelancers: €6,000. Two people on sales and marketing, fully loaded: €36,000. Total: €60,000.
- New paying customers over the quarter: 120.
- CAC = 60,000 ÷ 120 = €500 per customer.
- Counting ads alone would have given 18,000 ÷ 120 = €150 — a third of the real number. That gap is the most common CAC mistake.
€500 is neither good nor bad on its own. If those customers pay €50 a month and stay two years, it's excellent; if they pay €20 and leave within six months, it's a business that loses money on every sale.
Orders of magnitude
- There is no good CAC in absolute terms — only a CAC relative to what a customer brings back. The rule of thumb most SaaS investors quote is an LTV:CAC ratio of about 3:1: below it, growth eats margin; far above it, you are probably under-investing in acquisition.
- The more actionable number is CAC payback: how many months of gross margin it takes to earn the CAC back. Commonly cited targets are under 12 months for SaaS sold to small businesses, and up to 18-24 months in enterprise sales, where contracts are larger and longer.
- Paid CAC drifts upward over time on almost every channel: the cheapest audiences get won first, and auction prices rise. A CAC that stays flat while spend doubles is the exception, not the baseline.
How to improve it
- Fix activation and retention before spending more on acquisition: lower churn raises LTV, which makes the same CAC affordable — often the cheapest "CAC improvement" there is.
- Measure CAC per channel, not just blended. One channel usually hides another: a €150 SEO CAC and a €900 paid-social CAC average out to a number that describes neither.
- Work the conversion rate between the spend and the customer — landing page, sign-up flow, sales follow-up. Halving the drop-off after the click halves the CAC without touching the media budget.
- Build the channels that compound — content, referral, product-led loops — whose cost per customer falls as they grow, unlike paid media, whose cost rises.
In the Tour
Do you know your customer acquisition cost, even roughly?
- Yes, a solid number20 pts
- A rough estimate7 pts
- No idea0 pts
The Tour doesn't ask what your CAC is — it asks whether you know it. "A solid number" scores 20 on this question, "a rough estimate" 7, "no idea" 0, and the Acquisition stage score out of 20 averages this with your two other acquisition answers. A stage under 10 usually means the channel exists but nobody has priced it; that is where the Tour's verdict starts.
Questions people ask
Is CAC the same as CPA?
No. CPA (cost per acquisition) usually measures the cost of one action inside a channel — a lead, a sign-up, an install — and is reported by the ad platform. CAC measures the cost of one paying customer, across everything you spent. A €10 CPA on sign-ups with a 5% free-to-paid conversion is a €200 CAC before you add a single salary.
Should salaries count in CAC?
Yes — at least the share of the time spent winning new customers. Leaving them out is how a €500 CAC gets reported as €150. If the same people also look after existing customers, split their time and count only the acquisition share: an estimate is fine, zero is not.
How do I compute CAC when my sales cycle is three months long?
Lag the customers, not the spend: divide this quarter's spend by the customers who signed in the following quarter, or by the cohort that entered as leads this quarter and eventually closed. Either beats dividing today's spend by today's customers, which for a long cycle mostly measures last quarter's marketing.