How to Calculate Customer Acquisition Cost (CAC)

This guide covers the formula, the cost categories, worked examples and two related concepts: CAC payback period and the LTV:CAC ratio.

The CAC formula

CAC = Sales and marketing costs in the period ÷ New customers acquired in the period

Two rules make the result meaningful:

1. Same period, same scope. Costs and customers must come from the same time window and, if you calculate per channel, from the same channel.
2. New customers only. Repeat purchases by existing customers do not count as acquisitions.

Which costs to include

Cost category	Examples	Full CAC	Paid CAC
Ad spend	Search, social, display, sponsored listings	Yes	Yes
Agency and freelancer fees	Campaign management, design, copywriting	Yes	If related to paid channels
Tools	Email software, CRM share, analytics, scheduling tools	Yes	Optional
Content and creative	Photos, videos, articles, print materials	Yes	If used in ads
Events and trade fairs	Booth, travel, materials	Yes	No
Personnel	Share of salaries for marketing and sales work	Yes, if you can estimate it	No

Small businesses often leave out personnel costs because they are hard to allocate. That is acceptable as long as you are consistent and aware that the true CAC is higher. If the owner does all the sales calls, estimate the hours and apply a reasonable hourly value.

Blended CAC vs. paid CAC

Blended CAC divides all acquisition costs by all new customers, regardless of where they came from. It answers: what does growth cost us overall?

Paid CAC divides only paid channel costs by the customers won through paid channels. It answers: what does a customer from our ads cost?

Worked example (hypothetical): A software training provider has in one quarter:

• Ad spend: €4,500
• Agency fee for ads: €1,500
• Other marketing (newsletter tool, content, events): €2,000
• New customers from paid ads: 15
• New customers from organic search, referrals and newsletter: 25

Paid CAC: (€4,500 + €1,500) ÷ 15 = €400 Blended CAC: (€4,500 + €1,500 + €2,000) ÷ 40 = €200

Both numbers are correct and useful. The blended CAC looks lower because organic and referral customers are relatively cheap. If you only looked at blended CAC, you might overspend on ads believing each customer costs €200, when ad customers actually cost twice that.

CAC per channel

To compare channels, calculate CAC per channel. This requires reliable attribution of new customers to channels, which in turn depends on:

• Consistent UTM tags on all campaign links. Our UTM naming convention shows how to keep them clean.
• Recording the source of each new customer in your CRM, ideally both the tracked source and what the customer says when asked.

Channel	Costs	New customers	CAC
Google Ads	€3,000	10	€300
LinkedIn Ads	€3,000	5	€600
Newsletter	€400	6	€67
Trade fair	€2,500	4	€625

The figures are illustrative. A higher CAC is not automatically bad: if trade fair customers buy larger contracts, they may be worth it. That is why CAC must be compared with customer value.

CAC payback period

The CAC payback period tells you how many months it takes to earn back the acquisition cost from a customer's gross profit:

CAC payback (months) = CAC ÷ Monthly gross profit per customer

Example (hypothetical): CAC is €400, and a customer pays €100 per month for a service with a 60 % gross margin, so the monthly gross profit is €60. Payback: €400 ÷ €60 ≈ 6.7 months.

For small businesses, payback matters a lot because it shows how long cash is tied up in growth. A short payback lets you reinvest sooner.

LTV:CAC ratio

Customer lifetime value (LTV or CLV) is the gross profit a customer generates over the whole relationship. A simple estimate:

LTV = Average gross profit per month × Expected customer lifetime in months

The LTV:CAC ratio compares the two. In the example, if customers stay on average 24 months: LTV = €60 × 24 = €1,440, and LTV:CAC = €1,440 ÷ €400 = 3.6 : 1.

A ratio of about 3 : 1 is often quoted as a rule of thumb for a healthy balance, but treat it as orientation only. Whether a ratio is good depends on your margins, cash position, payback period and especially on how reliable your lifetime estimate is. New businesses often overestimate customer lifetime, so be conservative.

Calculating CAC quickly

For a quick calculation of CAC alongside ROAS and ROI for a campaign, use the marketing ROI, ROAS and CAC calculator: enter ad spend, other costs, revenue, margin and the number of new customers. For the difference between revenue-based and profit-based views, see ROAS vs ROI.

How to lower CAC

1. Improve conversion rates on landing pages and forms, so the same traffic produces more customers. See how to calculate conversion rate to measure it properly.
2. Improve lead quality with clearer targeting and messaging.
3. Follow up faster and more consistently, which raises the share of leads that become customers.
4. Invest in channels with compounding effects such as SEO content, email and referrals.
5. Cut channels with persistently high CAC and low customer value.

A simple monthly CAC routine

1. Export the sales and marketing costs of the month from your accounting system, grouped by channel.
2. Count new customers from your CRM or shop system, with their recorded source.
3. Calculate blended CAC, paid CAC and CAC for each channel you can attribute reliably.
4. Write the results into the same spreadsheet every month, next to the previous months.
5. Note one sentence explaining any large change, such as a new campaign, a price change or a seasonal effect.

After a few months, this simple table shows whether acquisition is getting more or less efficient, which matters more than any single month's figure.

Common mistakes

Including existing customers. Repeat orders do not count as new acquisitions.

Mismatched periods. Costs from one month and customers from another distort the result, especially with long sales cycles. Use longer periods or track the cohort of leads.

Only reporting blended CAC. It hides expensive channels.

Ignoring personnel costs without saying so. If you leave them out, note it, so nobody mistakes the figure for the full cost.

Comparing with other companies' CAC. Definitions differ widely. Compare with your own history and with customer value.

Summary

To calculate customer acquisition cost, divide sales and marketing costs by new customers from the same period. Decide which costs to include and stay consistent, calculate both blended and paid CAC, and break it down by channel where you can attribute customers reliably. Then compare CAC with customer value using the payback period and the LTV:CAC ratio. CAC is one of the central marketing KPIs for small business, and tracked monthly, it tells you whether growth is getting more or less expensive.