Measurement
Cost per lead, CAC and LTV: the three numbers to know before you hire marketing help
By the RelancR team · October 13, 2026 · 2 min read
Marketing help you cannot measure is marketing help you cannot judge. Three numbers do most of the work: cost per lead, customer acquisition cost and customer lifetime value. You can estimate each with a calculator and a spreadsheet.
Cost per lead (CPL)
CPL = marketing spend ÷ number of leads over the same period. Decide what counts as a lead (a form fill, a call, a qualified enquiry) and stick to it, or comparisons are meaningless.
Customer acquisition cost (CAC)
CAC = marketing and sales cost ÷ number of new customers over the same period. It is higher than CPL because most leads do not become customers. Include everything it took to win them: ad spend, fees or salaries, and the sales time.
Customer lifetime value (LTV)
LTV is roughly the gross profit a typical customer brings over the time they stay. Use profit, not revenue. For a one-off purchase it is simply the margin on that sale plus any repeat or referral business you can reasonably expect.
A worked example (illustrative only)
Suppose in one quarter you spend 6,000 in total on marketing and sales and get 120 leads and 12 new customers. CPL = 50. CAC = 500. If each customer brings about 1,500 in gross profit over their time with you, LTV = 1,500. LTV is three times CAC. These numbers are made up to show the arithmetic; yours will differ.
How to read them
- A frequently quoted rule of thumb is that LTV should be at least about three times CAC, but healthy ratios depend on your margins, sales cycle and cash position.
- Payback time matters as much: how many months of a customer's gross profit it takes to recover CAC. Long paybacks strain cash.
- Compare CPL and CAC by channel. An average hides channels that work and channels that waste money.
Mistakes that make the numbers lie
- Counting revenue instead of profit in LTV.
- Leaving out your own time, salaries or agency fees in CAC.
- Mixing periods: this month's spend against last month's customers when your sales cycle is long.
- Not tracking where leads came from, so every number is an average of everything.
What to do if you cannot calculate them yet
Start rough. Pull the last 90 days of marketing costs, count leads and customers, and write down your gross margin. A rough, honest number gives you something to improve; no number gives an agency or a hire nothing to be held to. Then set up source tracking so next quarter is better.
Measurement maturity is part of readiness
Whether you can state your cost per lead, CAC and LTV is one of the questions in the RelancR assessment, and a common reason marketing help stalls.
Frequently asked questions
What is a good cost per lead?+
There is no universal number. It depends on the value of a customer, your margins and how many leads become customers. Judge it against your own history and your CAC and LTV, not against someone else's average.
What is a good LTV to CAC ratio?+
A ratio of about three to one is often quoted as a healthy benchmark, but the right level depends on your margins, how long customers stay and how quickly you need to recover your spend.
How can I track where my leads come from?+
Add a "how did you hear about us?" question to forms and calls, use campaign tags on links you control, and record the source for every lead in your CRM or spreadsheet.
Can I calculate these without a CRM?+
Yes. A simple spreadsheet with spend, leads, customers and margin for the last 90 days is enough to produce rough numbers you can improve over time.
This article is general guidance, not professional advice. Every business is different, and nothing here guarantees a particular result.