Customer Acquisition Cost Calculator

Find out what each new customer really costs you to acquire.

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About this calculator

Customer acquisition cost (CAC) is what you spend, on average, to win one new customer. It is the number that decides whether your growth is sustainable: if a customer costs more to acquire than they will ever pay you, growth just accelerates your losses. Enter your marketing spend, your sales costs (salaries, commissions, tools) and the number of new customers acquired in the same period.

The formula

CAC = (Marketing spend + Sales costs) ÷ New customers

Worked example

Last quarter you spent £5,000 on marketing and £3,000 on sales, winning 120 new customers.

CAC = £8,000 ÷ 120 = £66.67 per customer

Common mistakes

Counting only ad spend and ignoring salaries, agency fees and tools.
Mismatching periods — spend from this month, customers from last month's campaigns.
Including returning customers in the count, which understates the true CAC.

Frequently asked questions

Relative to lifetime value: a common health benchmark is LTV of at least 3× CAC. A £70 CAC is excellent for a £1,000-LTV product and ruinous for a £50 one.

For an honest picture in an early-stage business, yes — cost your own selling time at a realistic rate.

Improve conversion rates (same spend, more customers), lean on referrals and content, and cut channels whose CAC exceeds their customers' value.

Assumptions & limitations

Assumes spend and customer counts cover the same period and that the customers counted are genuinely new.

Sources & verification

This calculator applies the standard formula published above to the figures you enter — it relies on no external statutory data. The formula and the worked example were checked by hand against each other.

Formula last verified: 24 July 2026

Maintained by: Steve Davis, Founder & Editor — see our editorial standards

Spotted an error or an out-of-date figure? Report it — corrections are prioritised over all other work (see our corrections policy).