CAC & Payback Calculator
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Work out what it costs to acquire a customer, how many months it takes to earn that money back, and — if you add churn — your LTV:CAC ratio. All calculated privately in your browser.
Why CAC is the other half of unit economics
Customer acquisition cost (CAC) is the fully-loaded price you pay to win one new customer: all the sales salaries, ad spend, agency fees, tooling and commissions for a period, divided by the customers those efforts brought in. LTV tells you what a customer is worth; CAC tells you what they cost to get. Neither number means much alone — together they tell you whether growth is creating value or burning it.
This calculator gives you three connected metrics in one place: CAC itself, the payback period, and (when you supply churn) the LTV:CAC ratio that investors and boards obsess over.
The formulas
The core calculation is simple, but the inputs matter. Use the same time window for both spend and customers, and include every cost that goes into acquisition — not just ad spend.
Payback tells you how long your cash is tied up before a customer becomes net-positive; a shorter payback means you can reinvest and grow faster on the same capital.
- CAC = total sales + marketing spend ÷ new customers acquired
- Monthly gross profit per customer = ARPU × (gross margin % ÷ 100)
- CAC payback (months) = CAC ÷ monthly gross profit per customer
- LTV = ARPU × (gross margin % ÷ 100) × (1 ÷ (monthly churn % ÷ 100))
- LTV:CAC ratio = LTV ÷ CAC
Reading the results, and common mistakes
A healthy SaaS business typically targets an LTV:CAC ratio of at least 3:1 and a CAC payback period under 12 months. A ratio below 1:1 means you lose money on every customer; a ratio far above 3:1 can actually be a warning that you are underinvesting in growth and leaving market share on the table.
The most common mistake is understating CAC — for example, counting ad spend but forgetting sales salaries and commissions, which makes acquisition look cheaper than it is. The second is comparing LTV against CAC using revenue rather than gross margin. Because our LTV already applies gross margin, the LTV:CAC here is an apples-to-apples, profit-based comparison.
Frequently asked questions
What should I include in sales and marketing spend?
Everything that drives acquisition for the period: paid advertising, content and SEO costs, sales team salaries and commissions, marketing tools, agencies and events. Leaving costs out inflates your apparent efficiency.
Which time period should I use?
Match the spend and the new-customer count to the same window — usually a month or a quarter. Mixing periods (a quarter of spend against a month of customers) produces a meaningless CAC.
Why is churn optional?
CAC and payback need only spend, customers, ARPU and margin. Churn is only required to estimate LTV and therefore the LTV:CAC ratio, so it is optional.
What is a good CAC payback period?
Under 12 months is generally considered healthy for SaaS; best-in-class companies recover CAC in under 6 months. Longer paybacks tie up more cash to grow.
Should CAC use blended or paid channels only?
Blended CAC (all customers, including organic) flatters the number; paid CAC isolates the cost of channels you actually pay for. Track both, but use paid CAC to judge advertising efficiency.
Is anything sent to a server?
No. Every figure is calculated locally in your browser and nothing you enter leaves your device.
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