How to calculate CAC
The formula is simple. The value is knowing what to count as spend, and reading the number against what a customer is worth.
By the GrowthCalc team · Updated June 2026
The CAC formula
Customer acquisition cost (CAC) is the average amount you spend to win one new paying customer. The standard formula is:
CAC = total sales and marketing spend ÷ new customers acquired
Both figures cover the same period. If you count the customers you won in a quarter, you divide by the spend from that same quarter. The two halves have to line up, or the answer is meaningless. The math itself is trivial. What separates a CAC you can trust from one that flatters you is the figure on top: what you actually count as spend.
What counts as acquisition spend
This is where most CAC numbers go wrong. People divide by ad spend alone and report a CAC that looks far healthier than reality. True acquisition cost is everything you put into winning a customer, beyond the media budget alone. Include the full cost of the team and tools doing the acquiring.
| Include in spend | Leave out |
|---|---|
| Paid ad spend across every channel | Cost of fulfilling or serving existing customers |
| Salaries of the marketing and sales people | Product, engineering and R&D costs |
| Agency, freelancer and contractor fees | General overhead unrelated to acquisition (rent, finance, legal) |
| Software and tools (ad platforms, CRM, analytics, email) | Customer support and account management |
| Content, creative and design production | One-off costs that did not win customers this period |
| Sales commissions and any referral or affiliate payouts | Retention and upsell spend on people you already have |
The simple test: if a cost exists to turn a stranger into a new customer, it belongs on top. If it exists to build the product or look after the customers you already have, it does not. Under-count this side and your CAC reads low, your budgets look safe, and you find out too late that you were buying customers at a loss.
A worked example
Say you spent 6,000 last month on acquisition (ad spend plus the share of salaries, tools and agency fees that went into winning customers), and that effort brought in 125 new customers.
6,000 ÷ 125 = 48
Your CAC is 48: it cost you 48 to acquire each customer. On its own that figure tells you nothing about whether the spend was worth it. Now bring in lifetime value. If each customer is worth 600 over their time with you, your LTV to CAC ratio is 600 ÷ 48 = 12.5:1, well above the 3:1 floor and clearly profitable. If a customer were worth only 40, the same 48 CAC would mean you lose money on every one you win.
What is a good CAC?
It depends entirely on lifetime value. There is no universal "good" CAC in cash terms, because 48 is excellent for a high-value customer and ruinous for a low-value one. The figure only makes sense relative to what a customer is worth.
The standard gut-check is the 3:1 LTV to CAC rule: keep CAC at or below a third of lifetime value, so a customer is worth at least three times what it cost to win them. The spare margin covers the cost of serving them and leaves a profit. As a quick read:
- LTV to CAC of 3:1 or higher is healthy: you earn back roughly three times your acquisition cost.
- Between 1:1 and 3:1 is thin: profitable on paper, but little room once you account for serving and overhead.
- Below 1:1 is unprofitable: you spend more to win a customer than they are worth.
Treat 3:1 as a widely used convention, not a law; the right target varies by industry, margin and growth stage. To work the relationship directly, use the LTV to CAC ratio calculator, and if you need to pin down lifetime value first, the LTV calculator turns order value, frequency and customer lifespan into a single number.
Common mistakes
- Counting ad spend only. Dividing by media budget alone ignores the salaries, tools, agency fees and content that did just as much acquiring. It is the most common way CAC ends up understated.
- Mismatched periods. Dividing this month's spend by last month's customers, or counting customers who were won by spend from an earlier period, breaks the ratio. Keep both halves in the same window.
- Mixing new and existing customers. CAC measures the cost to win new customers. Folding in retention and upsell spend, or counting returning buyers as new, distorts the figure.
- Reading CAC in isolation. A low CAC is not automatically good and a high one is not automatically bad. Without lifetime value beside it, the number cannot tell you whether the acquisition is sustainable.
Frequently asked questions
What formula is used for CAC?
CAC equals your total sales and marketing spend for a period divided by the number of new customers acquired in that same period. Spend covers everything you put into winning customers, beyond the ad budget alone, and the period for spend must match the period you count customers in.
What is CAC and how is it calculated?
CAC, or customer acquisition cost, is the average amount you spend to win one new paying customer. Calculate it by adding up all the sales and marketing costs in a period, then dividing that total by the number of new customers acquired in the same period. The number is only meaningful when you read it against the lifetime value of a customer.
What is a good CAC ratio?
There is no universal "good" CAC in cash terms; it depends on what a customer is worth. The common rule of thumb is to keep CAC at or below a third of lifetime value, which is the same as an LTV to CAC ratio of 3:1 or higher. At 3:1 you earn back roughly three times what it cost to acquire a customer. This is a convention that varies by industry, not a hard rule.