How to calculate customer acquisition cost

To calculate customer acquisition cost, add up everything you spent on marketing and sales in a period, then divide it by the number of new customers you won in the same period. If you spent $3,000 in a month on ads, management and tools, and won 20 new customers, your customer acquisition cost (CAC) is $150. That number tells you what it really costs to win one customer, which is the figure you need to decide whether your marketing is worth it.

The formula is simple. The hard parts are deciding what to include, counting customers honestly and knowing what CAC you can afford. Here is how to handle each.

The formula

CAC = total acquisition costs ÷ number of new customers

Use the same period for both sides: a month, a quarter or a year. For businesses with long sales cycles, a quarter is often more reliable than a single month, because a customer who enquired in March might only sign in May.

What to include in acquisition costs

Be honest here. Leaving costs out makes CAC look better than it is.

Usually included:

• Ad spend on Google, Meta and other platforms.
• Management fees for whoever runs the ads or SEO.
• Marketing software: CRM, email platform, call tracking, scheduling tools, to the extent they serve acquisition.
• Creative costs: photos, videos, design, copywriting for ads and landing pages.
• Sales commissions or referral fees paid for new customers.
• The share of staff time spent on marketing and sales, if someone on payroll handles it.

Usually left out, or tracked separately:

• Costs of serving existing customers, such as account management or support.
• One-time investments like a new website, which you can spread over its useful life (for example, a $3,000 website over three years adds roughly $83 a month).

Decide your rules once and keep them consistent, so you can compare month to month.

Counting new customers correctly

Count only new paying customers, not repeat purchases from existing ones and not leads who never bought. For businesses where quotes take weeks, count customers in the period they paid or signed, and be consistent.

To calculate CAC by channel, you need to know where each customer came from. Ask every new customer, track calls and forms with UTM tags and conversion tracking, and record the source in your CRM or spreadsheet. My guide to UTM tracking shows how to tag your links.

Three worked examples

These are illustrative numbers, not client data.

A residential cleaning company.

New recurring customers in the month: 18. CAC = $2,050 ÷ 18 = about $114.

A physiotherapy clinic. Ad spend $1,500, Meta ads management $700, and a part-time coordinator who spends about a quarter of her time on new-patient enquiries, roughly $800. Total $3,000. New patients: 25. CAC = $120.

A kitchen renovation company. Over a quarter: Google Ads spend $4,500, management $2,250, a photo shoot for the portfolio spread over a year adds $300, and showroom consultations take about $1,500 of the owner's time. Total $8,550. New contracts signed: 6. CAC = $1,425. That sounds high until you compare it with the average contract value, which is the point of the next section.

What CAC can you afford?

CAC on its own means nothing. A $1,425 CAC is excellent for a kitchen renovation and disastrous for a haircut. Compare it with what a customer is worth:

• Gross profit from the first purchase. If CAC is lower than this, every new customer pays for itself immediately.
• Customer lifetime value. If customers come back, a CAC higher than the first purchase's profit can still be very profitable. My article on customer lifetime value shows how to estimate it.

A common rule of thumb is that lifetime value should be at least three times CAC, but treat this as a sanity check, not a law. Margins, cash flow and how quickly customers pay back all matter.

A practical way to set your limit: decide what share of the first-year gross profit from a customer you are willing to spend to win them. That figure becomes your maximum CAC, and your marketing should aim to stay well under it.

How to lower CAC

CAC goes down either by spending less per lead or by converting more leads into customers. The second is often easier.

• Respond faster. Leads that hear back within minutes convert far better than those that wait until tomorrow.
• Follow up on quotes. A friendly reminder after a few days recovers customers who simply got busy.
• Improve the landing page. More enquiries from the same clicks lowers cost per lead directly.
• Cut wasted spend. Irrelevant search terms, wrong locations, audiences that never buy.
• Grow referrals and reviews. Customers who arrive through a referral cost almost nothing to acquire.
• Shift budget between channels. Once you have CAC by channel, move money towards the cheapest source of good customers.

If your CAC on Google Ads seems too high, a Google Ads audit is usually the quickest way to find wasted spend.

Common mistakes when calculating CAC

• Counting leads instead of customers. Dividing spend by enquiries gives cost per lead, a different number.
• Ignoring management fees and software. Ad spend alone flatters the result.
• Mixing periods. Spend from one month divided by customers from another produces nonsense, especially in seasonal businesses.
• Calling referrals free. They are cheap, but if you pay referral fees or give thank-you gifts, include them.
• Averaging everything together. A blended CAC can hide one excellent channel and one terrible one. Split it by source as soon as your tracking allows.
• Judging too early. A new campaign often has a high CAC in its first weeks while it learns. Give it enough time and data before deciding.

Track it monthly

Add CAC to the short list of numbers you check every month, ideally by channel. It works best alongside leads, conversion rate and revenue from new customers, which I cover in the 7 marketing numbers to check monthly. Watching the trend matters more than any single month: a CAC slowly rising over a quarter is an early warning that something in your marketing or sales needs attention.