one-line definition
CAC is a core operating metric that helps small teams make better product and growth decisions.
formula: CAC = Total acquisition spend ÷ Number of new customers
tl;dr
CAC is what you spend to get one paying customer. If you don't know this number, you can't tell whether a channel is profitable or bleeding money.
Simple definition
CAC (Customer Acquisition Cost) is the total amount you spend to acquire one new paying customer. Add up everything you spent on marketing and sales in a given period, then divide by how many customers you signed up. That includes ad spend, content creation costs, tools, freelancers -- anything directly tied to getting new users through the door.
For bootstrapped builders, CAC is the reality check on your growth strategy. A channel with a $15 CAC and a channel with a $200 CAC tell very different stories, even if they bring the same volume.
How to calculate it
CAC = Total acquisition spend / Number of new customers
Say you spent $2,400 on Google Ads, $600 on a freelance writer for SEO posts, and $200 on email tool costs in January. You got 40 new paying customers.
CAC = ($2,400 + $600 + $200) / 40 = $3,200 / 40 = $80
Break it down by channel too. If 25 of those customers came from ads ($2,400 / 25 = $96) and 15 came from organic content ($800 / 15 = $53), you know where to double down.
Example
You sell a $49/month SaaS tool. You try two channels: Twitter ads and a free tool on your website. Twitter ads cost $1,200/month and bring 8 customers (CAC = $150). The free tool cost $400 to build and brings 12 customers per month through organic search (CAC = $33 after month one, trending toward $0 as the build cost amortizes). The free tool has 4.5x better unit economics. Stop scaling the ads. Pour energy into building more free tools and writing about them.
Related reading
Related terms
- MRR
- CAC
- LTV
FAQ
Why does CAC matter?+
It gives a fast signal about whether your product and distribution system is improving or regressing.