Daily Junction.mobi portalMarketing · April 21, 2026 · Harper Quinn · 5 min
Customer acquisition cost, lifetime value and payback period together tell you whether your marketing makes money. Here is how to calculate each, what healthy ratios look like, and a worked example.
Most arguments about whether marketing is "working" go in circles because the people having them are looking at the wrong numbers — impressions, clicks, likes. Three figures cut through the noise and tell you whether your marketing actually makes money: customer acquisition cost (CAC), lifetime value (LTV) and payback period. Together they reveal whether each pound you spend winning customers comes back, how much it brings, and how quickly. Master these and you can defend a budget, fix a leaky funnel and decide where to invest with confidence.
CAC tells you the price of growth. LTV tells you what that growth is worth. Payback tells you how long your cash is tied up before it comes back. You need all three; any one alone can mislead.
CAC is the most straightforward — and the most often understated:
CAC = (total sales and marketing costs in a period) ÷ (new customers won in that period)
The trap is leaving things out. A true CAC includes ad spend and the salaries of the people running campaigns, software and tools, agency fees and creative costs. Count only the ad spend and you will flatter yourself badly.
LTV should be built on gross profit, not revenue, because revenue ignores the cost of actually delivering your product:
LTV = (average gross profit per customer per period) × (average number of periods a customer stays)
For a subscription business that is roughly monthly margin multiplied by the average number of months a customer stays before they churn. For a one-off purchase it is the gross profit per sale multiplied by the average number of repeat purchases over time.
Payback period ties the two together in time:
Payback (months) = CAC ÷ (monthly gross profit per customer)
A short payback means your acquisition spend returns quickly and can be recycled into more growth. A long one means cash is locked up for months before it returns — fine if you have deep reserves, dangerous if you do not.
The single most-quoted benchmark is an LTV:CAC ratio of about 3:1 — each customer is worth roughly three times what it cost to acquire them. The logic: that multiple has to cover acquisition, the cost of serving the customer, overheads and still leave a profit.
| LTV:CAC ratio | Rough interpretation |
|---|---|
| Below 1:1 | You lose money on every customer — unsustainable |
| Around 1–2:1 | Thin; little margin to fund the rest of the business |
| Around 3:1 | Often considered healthy and balanced |
| Well above 5:1 | Efficient — but you may be underinvesting in growth |
That last row surprises people. A very high ratio is not automatically a triumph; it can mean you are leaving growth on the table by spending too cautiously, and a competitor willing to invest more aggressively may take the market.
On payback, many businesses aim to recover CAC within around 12 months, though the right target depends entirely on your margins and how much cash you can afford to have tied up. These are rules of thumb, not laws — they vary widely by industry, business model and stage. Treat them as a starting point for judgement, and compare against realistic small-business marketing benchmarks for your sector rather than chasing a single magic number.
Suppose an online services business spends, in one quarter:
That is £13,000 of acquisition cost, and it wins 100 new customers.
CAC = £13,000 ÷ 100 = £130 per customer
Each customer pays £30 a month, and the gross margin (after the cost of delivering the service) is 60%, so each brings £18 of gross profit per month. On average customers stay 24 months.
LTV = £18 × 24 = £432 per customer LTV:CAC = £432 ÷ £130 ≈ 3.3:1 — healthy Payback = £130 ÷ £18 ≈ 7.2 months — comfortably under a year
This business is in good shape: it earns back acquisition costs in about seven months and each customer is worth more than three times what they cost. That gives it confidence to spend more on acquisition, because the maths works.
Once you track these three figures, they change how you make decisions:
Discipline around these metrics is exactly what separates effective marketing from expensive marketing. London consultancy CM Beyer makes the same case in its breakdown of the three numbers that decide whether your marketing works, arguing that without them you are essentially guessing. And tying spend back to outcomes is the foundation of being able to measure marketing ROI at all.
CAC, LTV and payback period are the three numbers that turn marketing from a cost you hope is working into an investment you can prove is working. Calculate CAC fully (not just ad spend), base LTV on gross profit, and watch the payback period as closely as the LTV:CAC ratio. Aim for roughly 3:1 and a payback inside a year as a starting point — then use the numbers to diagnose, decide and grow.
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