CAC Calculator
Customer acquisition cost is the first number that tells you whether growth is a machine or a leak. Enter what you spent and how many customers it bought — then add lifetime value to see the only ratio investors really care about.
CAC = total sales & marketing spend ÷ new customers acquired. On its own it is just a price tag; paired with lifetime value it becomes the LTV:CAC ratio, the clearest read on whether your economics scale. A 3:1 to 5:1 ratio is the widely used sign of a healthy business; below 1:1 you lose money on every customer, and far above 5:1 you are probably underinvesting in growth.
CAC Calculator inputs and result
| Ratio | What it means |
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How to use this calculator
- Add up fully-loaded acquisition spendInclude everything that won the customers: media, the salaries of the people running it, tools, agency fees, and commissions. A spend number that omits salaries flatters your CAC.
- Count only new customersUse net new customers from the same period as the spend. Mixing renewals or existing buyers into the count understates your true cost to acquire.
- Add lifetime value for the verdictEnter the gross-profit lifetime value of a customer. The tool turns CAC into the LTV:CAC ratio, which is what actually tells you if the economics work.
- Read the ratio against the bandsUse the table: under 1:1 you lose money, 3:1 to 5:1 is healthy, and well above 5:1 usually means you are underinvesting in growth.
- Export your numbersCopy a share link, download the CSV for your model, or print a one-page PDF for the budget conversation.
RGM Expert Says
We open almost every growth engagement with this number, because CAC is where optimism meets arithmetic. A founder will describe a channel as ‘working’ and then discover, once salaries and tools are loaded in, that the true cost to acquire is double the media number they were quoting. Getting CAC honest is step one; everything downstream — budget, hiring, fundraising — rests on it.
The tool earns its keep by forcing the LTV pairing. CAC in isolation invites the wrong fight (‘make it lower’); the LTV:CAC ratio reframes it as the right one (‘make the relationship better’). Sometimes the best move is not a cheaper click but a stickier product or a higher price. We use the ratio bands to decide which lever to pull: thin ratios usually mean a retention or monetization problem, not a media one.
The most useful moment is when the ratio comes back above 5:1 and a client assumes that is good news. Often it means they are starving a profitable channel. We use that reading to make the case for spending more — the rare growth recommendation a CFO is happy to hear, because the math is right there.
How it works
CAC is deliberately blunt: the total cost of acquiring customers divided by the number you acquired.
- Sales & marketing spend — fully loaded: media, people, tools, agencies, commissions.
- New customers — net new in the same period as the spend.
- LTV — gross-profit value of a customer over their lifetime; pair with CAC for the ratio.
The 3:1 LTV:CAC benchmark and the sub-12-month payback guideline are popularized in David Skok’s widely cited SaaS Metrics 2.0.
CAC alone can lie; the ratio tells the truth
A low CAC looks like a win until you learn the customers churn in two months. A high CAC looks alarming until you learn each customer stays for years. That is why the LTV:CAC ratio, not CAC, is the number that predicts whether a business compounds. The widely cited rule of thumb — roughly 3:1 with payback inside a year — comes from David Skok’s SaaS Metrics work and has become the default lens for operators and investors alike.
The second trap is blended vs. paid CAC. Blended CAC (all new customers, including organic and word-of-mouth) flatters paid performance by crediting it with customers it did not buy. For budget decisions, isolate paid CAC by channel; use blended CAC only for the whole-business view. Our blended CAC calculator handles that split.
Finally, CAC is a planning input, not just a scorecard. Once you know your CAC and your target ratio, you can work backward to an allowable CAC — the most you can pay per customer and still hit your margin — and hold every channel to it.
How to read the LTV:CAC ratio
There is no universal ‘good’ CAC — it depends entirely on lifetime value. The ratio, not the dollar figure, is the benchmark that travels across industries.
| LTV : CAC | Interpretation | Typical action |
|---|---|---|
| Below 1 : 1 | Unprofitable acquisition | Fix LTV or CAC before scaling |
| 1 : 1 to 3 : 1 | Thin margin for growth | Improve retention or efficiency |
| 3 : 1 to 5 : 1 | Healthy, scalable | Scale with confidence |
| Above 5 : 1 | Underinvesting | Consider spending more |
What operators say about CAC
The LTV:CAC ratio is one of the most important metrics for any subscription business; a ratio around 3:1 is a strong, capital-efficient target, with payback ideally under twelve months.
Sustainable growth comes from a repeatable, profitable acquisition loop — not from buying customers faster than they pay you back.