The full CAC breakdown + the sheet to track it.

CAC, customer acquisition cost, is what you spent to win new customers in a month, divided by the number of new customers you won that month.

CAC = what you spent to win customers ÷ new customers won

It isn’t your cost per lead or your cost per click. A lead who never buys still costs you money but never makes it into the bottom of that sum. That’s why CAC is the number that tells you whether your marketing pays.

• Count new customers only. A regular coming back is good news, but you didn’t pay to win them this month.
• Use the same month for both numbers. October’s spend, October’s new customers.

The top of the sum is every cost of winning customers. Write your list once and keep it the same every month, or the trend won’t mean anything.

• Ad spend on every platform: Meta, Google, TikTok and anything else.
• Agency, freelancer and content fees.
• Marketing tools: your CRM, your email and text platform, design apps.
• First-visit discounts and free offers, if you use them to win new customers.

Your own time is optional. If you count it, give it an hourly rate and count it every month.

Two versions are worth tracking. Blended CAC uses all of the costs above and all new customers. Paid CAC uses ad spend only, and only the customers who came from ads. If you can’t yet tell which customers came from ads, start with blended: guide 002 sets up the tracking that makes paid CAC possible.

Take the count from the place the sale actually happens: your booking calendar, your CRM, your Shopify orders or your signed contracts. Not from the ad platform.

Ad platforms report the conversions they give themselves credit for, under their own rules about clicks and views. That’s useful for comparing one ad with another. It isn’t your customer count.

• Salon or clinic: a first visit from a client who has never booked with you before.
• Online store: a first order from an email address that hasn’t ordered before.
• Home services: a signed job from a homeowner you haven’t worked for before.

Download the sheet. It has a row for every month and does the division for you: fill in your spend and your new customers, and your blended and paid CAC appear on their own, with a year-to-date total at the bottom. It takes about ten minutes on the first working day of the month.

Or start your own: copy these columns into any spreadsheet, one row per month.

Month	Ad spend	Fees and tools	Total spend	New customers	Blended CAC	New customers from ads	Paid CAC	First-sale profit	Notes

Blended CAC = Total spend ÷ New customers. Paid CAC = Ad spend ÷ New customers from ads. Use Notes for anything that explains a jump: a holiday, a new offer, a week the phone wasn’t answered.

A $125 CAC is cheap for a roofing company and expensive for a coffee shop. The number only means something next to what a new customer earns you. Work out two figures:

1. First-sale profit: the price of the first sale, minus what the product or the job cost you, minus card fees.
2. 12-month profit: the first sale plus the repeat visits or orders an average customer makes in a year, after the same costs. Your booking system or Shopify customer report has the repeat rate.

• CAC below first-sale profit: every new customer pays for themselves on day one.
• CAC between the two: you pay for growth up front and earn it back over the year. That works as long as you can carry the gap.
• CAC above 12-month profit: spending more makes the problem bigger, not smaller. Fix the leak before you add spend.

Payback in months = CAC ÷ monthly profit per customer. The longer it takes, the more cash you need on hand to keep growing.

One month is noisy. A slow week, a holiday or one big job moves it. Look at the last three months together, and if your business is seasonal, compare each month with the same month last year.

• CAC rising while spend stays flat: something between the first contact and the sale is leaking. Guide 003 covers that.
• CAC falling while spend rises: rare, and worth protecting. Find what changed and write it down.
• Fewer than 10 new customers a month: use a three-month total instead of single months.