You can know how much you spend on advertising and still not know what a new customer really costs. The agency fee, sales time and follow-up tools may sit in different parts of the business, while customers close weeks after they first enquire.
Customer acquisition cost for a service business brings those costs together. The basic calculation is simple: relevant marketing and sales spending divided by new customers acquired. The care is in deciding what belongs in the calculation and matching it to the right customers. I would make those definitions clear before using the figure to increase or cut a budget.
In this guide
Choose the costs you will include
Begin with the costs directly involved in attracting and winning new customers. That can include advertising, campaign management, sales-related software and the acquisition share of staff time. If a new page was built for the campaign, decide how you will account for that setup cost too.
There is nothing wrong with also looking at a narrower number, such as advertising spend per customer. Just name it accurately. A media-only calculation and a fully loaded acquisition calculation answer different questions, so they should not share an unexplained label.
Use one method consistently. If you include sales time this month but omit it next month, an apparent improvement may simply be a change in counting. Write the method beside the report so anyone reviewing it can understand the result.
Keep existing-customer purchases separate. If a client buys again, that revenue matters, but it is not usually another newly acquired customer. Mixing repeat orders into the denominator can make acquisition look cheaper than it actually is.
Use the formula with a clear denominator
CAC = acquisition costs ÷ new customers acquired. In a hypothetical month, £2,400 of advertising and fees plus £600 of sales time creates a £3,000 acquisition cost. If ten new customers are won from that activity, CAC is £300. You can repeat the calculation with your own costs and customer records.
If no customers have yet closed, do not divide by zero or present a reassuring estimate as a result. Report spending and pipeline progress, then calculate CAC when outcomes are known. For a small number of wins, show the customer count alongside the figure; one large contract can change the apparent picture dramatically.
Match costs to the sales cycle
A same-month calculation can mislead when prospects take several weeks to buy. Track a cohort of enquiries from a particular period and update its customer count as sales mature. You can also report a rolling period, provided you explain its limitations and avoid mixing unrelated campaigns.
Keep the original source in your CRM and record won dates. Attribution is rarely perfect: someone may see an advert, read a blog and later call directly. Use a consistent attribution rule and report uncertainty rather than pretending every sale has one unquestionable source.
Compare CAC with contribution, not just revenue
A £300 acquisition cost may be reasonable for a profitable recurring contract and unsustainable for a small one-off job. Compare the cost with contribution after direct delivery costs. Consider when money is collected and how long the customer typically stays; do not assume a full year’s retention without evidence.
Calculate different services separately when their margins and sales cycles differ. Then improve the bottleneck: unsuitable leads, delayed responses, weak quotes or poor close rates. Cutting advertising blindly may reduce profitable demand without fixing the underlying issue. Read CPL versus CAC and how to plan a service-business marketing budget.
How the number changes a budget decision
Imagine a service business spends £3,000 to win ten new customers. Its acquisition cost is £300 per customer, using the costs included in that example. The next question is not whether £300 sounds high or low; it is what each customer contributes to the business.
A recurring contract may generate useful contribution over time, while a small one-off job may not recover the same acquisition cost. Check direct delivery costs, likely repeat work and when cash is collected. Use observed retention where available rather than assuming every customer stays for a full year.
Also look at the service mix. If eight customers buy a low-margin service and two buy a much stronger contract, a single average can hide the difference. Separate the figures when that helps you decide which work to promote.
Then inspect the funnel. If suitable enquiries arrive but quotes are slow, improving the sales process may reduce acquisition cost without reducing advertising. If the team spends time on unsuitable requests, better offer clarity may help.
I would use CAC as a conversation starter, not a verdict delivered without context. It should lead to questions about customer fit, timing and the process. Keep the customer count visible because a small number of wins can make the figure move sharply.
For help connecting the costs and records, fill out the customer acquisition plan form. Tell us what you spend, how enquiries are handled and which customer outcomes your team can currently identify.
Frequently asked questions
Should I include the salesperson’s salary?
Include the acquisition-related share for a fully loaded CAC. Document the allocation so comparisons remain consistent across periods.
Is there a universally good CAC?
No. A sustainable figure depends on contribution, repeat business, retention and cash flow. Compare it with your own economics and credible historical data.
Can I calculate CAC by channel?
Yes, when costs and customer sources can be matched reasonably. Keep the same source rules and explain where a cost is shared between channels.
Ready to work on this for your business?
If you would like me and the DIL team to help you put this into practice, fill out the customer acquisition plan form. Tell us where you are now and what you want to improve, so we can start with your situation.