What Is Customer Acquisition Cost (CAC)?
Customer acquisition cost is what you spend to win one new customer. Here's how to calculate CAC, what counts, and how to read it against the value of a customer.
What it is
Customer acquisition cost, or CAC, is the total amount you spend to win one new customer. Not one lead — one paying customer. It rolls up everything it takes to turn a stranger into someone who hands you money: the ads, the lead fees, the software, and the hours spent following up and closing.
If cost per lead measures the front door, CAC measures the whole trip from “interested” to “paid invoice.” That makes it one of the most honest growth numbers a contractor can track, because it includes the leads that didn’t pan out. You paid for those too.
How to calculate it
The formula is simple:
Total sales and marketing spend ÷ new customers won = customer acquisition cost
Say in a month you spent $4,000 across ads, lead services, and your scheduling software, and that effort won you 10 new customers. Your CAC is $4,000 ÷ 10 = $400 per customer.
The judgment call is what you put in the numerator. A complete CAC includes:
- Ad spend and lead-service fees
- Marketing software and subscriptions
- The cost of time spent selling — yours or a salesperson’s
- Any setup or onboarding costs tied to winning customers
Leave the time out and your CAC looks artificially low. For a small shop where the owner does the selling, that time is real money — it’s hours not spent on the tools. You don’t have to be precise to the penny, but be consistent so the number means the same thing month to month.
Like cost per lead, calculate CAC per channel when you can. A blended number across every source hides which channels win customers cheaply and which ones drain the budget.
Why it matters for contractors
CAC matters because it tells you the true price of growth. Plenty of contractors know roughly what a lead costs but have never worked out what a customer costs — and those are wildly different numbers once you account for the leads that go nowhere.
Here’s the key idea: a high CAC isn’t a problem on its own. What matters is the gap between what it costs to win a customer and what that customer is worth to you. Spending $400 to win a customer who brings you $5,000 over time is a fantastic trade. Spending $400 to win a one-time $300 job is a slow way to go broke. CAC only becomes meaningful when you set it next to the value of a customer — which is exactly what lifetime value measures.
This is also why chasing the cheapest leads can backfire. If a bargain channel sends leads that rarely close, you burn spend on dead ends, and your CAC climbs even though your cost per lead looked great. The customers you do win end up carrying the cost of all the ones you didn’t.
Common mistakes
- Counting leads instead of customers. CAC is per customer won, not per lead generated. Mixing them up makes growth look far cheaper than it is.
- Leaving out your own time. If you’re the one selling, your hours belong in the math. A “free” sales process isn’t free.
- Ignoring the leads that didn’t close. Every dollar spent on leads that went nowhere is part of the cost of the customers you did win. CAC counts them; cost per lead doesn’t.
- Reading CAC in a vacuum. A number with no context is just anxiety. Always compare it to what a customer is worth before deciding it’s too high.
- Using one blended CAC. Average every channel together and you’ll keep funding the expensive ones because the cheap ones make the total look fine.
How it relates to consent-first leads
The fastest way to wreck your customer acquisition cost is to pour money into leads that don’t close — shared leads sold to four contractors, recycled lists, people who never agreed to hear from you. You pay for all of them, and only a sliver become customers, so your CAC quietly balloons.
Consent-first leads attack the problem from the other side. When the person agreed to be contacted on a channel they chose, and the lead is exclusively yours, more of them answer and more of them book. Fewer wasted leads means a lower cost per customer won. At a flat, predictable price per lead, you can actually forecast your CAC instead of guessing at it — and that’s what lets you grow on purpose instead of by luck.