The short definition
Customer acquisition cost (CAC) = total spend on winning customers ÷ new customers won.
Spend $3,000 across advertising and marketing in a month and win 15 new customers, and CAC is $200.
What to include
Be consistent, and lean toward including more rather than less:
- Advertising spend
- Agency or retainer fees
- Software directly used for acquisition
- Time spent selling, if you can attribute it
What to leave out: costs of serving customers you already have. Retention is a different budget answering a different question.
Counting only ad spend produces a flattering number that will lead you to overestimate how well acquisition is working.
The comparison that matters
CAC on its own means nothing. It only means something against lifetime value — what a customer is worth across their whole relationship with you.
If a customer is worth $900 in gross profit over three years and costs $200 to acquire, that is a healthy business. If they are worth $180, it is not, however good the campaign reports look.
A rough rule used widely is that lifetime value should be comfortably above acquisition cost — comfortably enough to cover overhead and the customers who do not return.
The first-job trap
Many service businesses compare CAC against first-job value alone. That is the most common reason a business decides it cannot afford to advertise.
If customers come back — annual service, maintenance plans, repeat repairs, referrals — the first invoice understates the truth, sometimes several times over. Businesses that only count the first job systematically under-invest and then cannot understand how competitors afford to outspend them.
Calculate it by channel
A blended CAC hides the whole picture. One channel may acquire customers at $90 and another at $600, and the average tells you to do nothing in particular.
By channel, it tells you exactly where the next dollar goes.
What lowers it
A better close rate. Free, immediate, and it lowers CAC proportionally.
Faster response. The largest single driver of close rate in service businesses.
Referrals. Close to zero acquisition cost and the highest close rate you will get. Chronically under-encouraged.
Reviews. They lower the cost of every click before anyone speaks to you.
Repeat business. Not strictly acquisition, and it raises lifetime value, which achieves the same thing.
Working yours out
Take last quarter's marketing spend and count the new customers. That is your starting number — then break it down by source.
Frequently asked questions
How is customer acquisition cost calculated?
Total spend on winning customers divided by new customers won. Include advertising, agency fees, acquisition software and attributable selling time — not the cost of serving existing customers.
What should I compare it against?
Lifetime value — what a customer is worth across the whole relationship. CAC alone means nothing; the ratio between the two is what tells you whether the business works.
What is the first-job trap?
Comparing acquisition cost against a single invoice when customers actually return for years. It is the most common reason a service business concludes it cannot afford to advertise.
What lowers acquisition cost fastest?
A better close rate, driven mostly by faster response. Then referrals, which cost almost nothing and close best, and reviews, which lower the cost of every click before anyone speaks to you.