CAC calculator

CAC is what it costs on average to win one new customer: sales and marketing spend in a period divided by the new customers won in it.

The formula

CAC = sales and marketing spend ÷ new customers

Worked example: £300 a customer

The example is a UK software company in one month: £50,000 of revenue excluding VAT, 400 customers and £180,000 in the bank.

£9,000 ÷ 30 new customers = £300

Try it with your numbers

Work out your CAC

It starts on the example. Replace any figure with your own; nothing you type leaves your browser.

Your business numbers

Start with any one figure. Each one you add works out more below. Your numbers are kept in this browser only.

What this calculation uses

Sales and marketing (needed)

Ads, sales salaries and tools.

New customers (needed)

Add more of your numbers

Open a group to fill it in. Everything you add shows up in the list below the calculator.

Sales and VAT

MonthQuarterYear

Turnover

Everything you invoiced in the period.

My turnover includes VAT

20%5%None

VAT you reclaim on costs

Input VAT on your purchases in the period.

Of which recurring

Subscriptions and contracts, excluding VAT.

Value of orders through your platform

Marketplaces only: what buyers paid in total.

Costs

Cost of sales

Costs that grow with each sale: materials, hosting, payment fees.

Staff costs

Salaries, employer National Insurance, pensions, freelancers.

Other running costs

Rent, software, insurance, admin.

Depreciation and amortisation

From your accounts. 0 if you have none.

Interest paid

Corporation Tax

For the period, if you pay any.

Equipment and other capital spending

Things that last more than a year.

Customers and orders

Customers at the start

Customers lost

Number of orders

Or invoices, for a service business.

Recurring revenue over one month

MRR at the start of the month

Upgrades

Extra MRR from existing customers.

Downgrades

MRR lost from customers who left

Growth

Revenue this month

Revenue last month

Revenue this quarter

Revenue last quarter

Revenue this year

Revenue last year

Cash

Cash in the bank

Cash received from customers

In the period, not what you invoiced.

Cash paid out for running costs

In the period, not counting equipment.

Balance sheet

Everything the company owns

Cash, equipment, money owed to you.

Everything it owes

Loans, bills, tax due.

Team

Hours your team works a week

Everyone added together.

Full-time hours a week

One investment or campaign

What you spent

On a campaign, a hire or a piece of kit.

What it brought back

Extra gross profit it produced.

Your CAC

£300

a customer

£9,000 ÷ 30 new customers = £300

Formula: Sales and marketing spend ÷ new customers.

CAC payback: 3.6 months; months of gross profit to earn it back

How to read your result

CAC only means something next to what a customer is worth. The payback figure shows how many months of gross profit it takes to earn the cost back.

Watch out for

Include sales salaries and tools, not only ads. Ads-only CAC looks better, but it is not what investors mean.

Last checked 24 October 2026. Estimates only, not financial, tax or legal advice: check your accounts and documents, and take advice before you act. More terms in the startup glossary.