LTV:CAC Ratio: What Can You Afford to Pay for a Customer?

An LTV:CAC ratio can look healthy while the business runs short of cash. The customer may be profitable over twelve months, but the advertising, stock and fulfilment bills arrive before most of that value does.

Use the ratio to compare customer contribution with the complete cost of acquisition. Then check how long the contribution takes to arrive and whether the next customer is likely to behave like the customers already measured. A ratio is a useful test of the economics. It is not, by itself, permission to increase spend.

By David Black, founder of PureRapid. Editorial analysis; sources checked 21 October 2026.

Define the LTV:CAC ratio before comparing it

Customer lifetime value, or LTV, has several definitions. For acquisition decisions, use contribution value: customer revenue after refunds, discounts and the variable costs of serving those orders, before the original acquisition cost. State the observation period.

Customer acquisition cost, or CAC, is the cost allocated to winning new customers divided by the number of new customers acquired. Include paid media and the relevant share of creative, management, tools and internal acquisition work. Record the allocation method and count each cost once.

Contribution LTV:CAC = contribution per acquired customer over the stated period ÷ complete acquisition cost per new customer.

Revenue LTV can be useful for a revenue analysis, but a £100 sale is not £100 available to pay for acquisition. Equally, contribution is not net profit. Fixed overhead, financing and tax still need to be covered.

Measure equal-age groups of customers

Group customers by when they first bought. Follow all customers in each group, including those who never return. Measure cumulative net sales and costs at comparable ages, such as 30, 90, 180 and 365 days.

Do not divide repeat-customer revenue only by repeat customers and call the result the value of every acquired customer. That removes the people who did not come back and overstates the acquisition case.

Nor should a recent cohort inherit a twelve-month forecast without a visible assumption. Separate observed contribution from expected future contribution. If the measurement ends at twelve months, label it twelve-month contribution value; do not imply that the entire customer lifetime has been observed. Product mix, discounting, channel mix and customer intent can change the pattern.

Shopify’s customer reports include cohorts based on first order. Check the selected definitions and reconcile revenue with costs. A projected spend field is not audited profit or a promise of future purchases.

A 1.6:1 ratio, with a £12 first-order gap

Illustrative example, not a PureRapid client result. Suppose one acquisition cohort contains 500 new customers. Paid media and all allocated acquisition costs total £20,000, so complete CAC is £40.

The first orders leave £14,000 contribution before acquisition, or £28 per customer. By day 90, cumulative contribution reaches £23,000, or £46 each. By twelve months, it reaches £32,000, or £64 each. The twelve-month contribution-to-CAC ratio is £64 ÷ £40 = 1.6:1.

These figures exclude recoverable VAT. Contribution includes product or delivery costs, fulfilment, payment fees, refunds and allocated variable retention costs. Acquisition includes relevant media, creative, management and tools once. Fixed overhead, financing and tax are excluded.

The observed checkpoints show contribution payback occurred after the first orders and by day 90. They do not reveal the exact day. A simple CAC divided by average monthly contribution calculation would smooth away the purchase pattern that matters here.

Contribution payback is not cash payback

The £6,000 first-order deficit is part of the funding requirement. It is not the whole cash requirement. Stock may have been paid for earlier; customers may use payment terms; refunds and supplier settlements may arrive later.

Build a separate cash schedule from actual payment dates. The business must fund the largest cumulative cash shortfall, with room for uncertainty. A cohort can pass the contribution test while still demanding more working capital than the business can provide.

Turn the ratio into a ceiling for the next customer

Start with the contribution the business needs to retain after acquisition. In the example, suppose it requires £20 per customer towards fixed overhead and profit over twelve months. The value-based CAC ceiling becomes £64 − £20 = £44.

Now add a funding constraint. Suppose the owner requires contribution payback within 90 days. The observed £46 by that point gives a separate £46 ceiling before an uncertainty allowance. The tighter of £44 and £46 is £44.

This is a planning limit, not a spending target. If twelve-month contribution falls by 20%, it becomes £51.20. Keeping the same £20 requirement cuts the value-based ceiling to £31.20. The earlier £40 CAC would no longer meet that requirement.

Choose your own period and retained contribution. A business with limited cash may need first-order payback. Another may reasonably fund a longer return when repeat purchasing is well evidenced and the cash exposure is affordable.

A reusable acquisition-ceiling worksheet

Copy these fields into your working notes. Use one mature cohort and one consistent cost basis. Keep the supporting order and cost records so another person can reproduce the result.

Now repeat the calculation with a defensible downside. If the 12-month value is 20% lower, the value ceiling is £31.20. If day-90 contribution is also 20% lower, that ceiling is £36.80, so £31.20 still governs. Write the assumption beside the result; do not treat the percentage as a standard buffer.

The worksheet is undefined when there are no acquired customers. A negative value ceiling means the required retained contribution is not supported even before acquisition. Neither result should be converted into permission to spend. Cash timing, capacity and the value of the next cohort can impose a tighter limit again.

Is 3:1 a good LTV:CAC ratio?

It depends on what sits inside both numbers, how long value takes to arrive and what must be paid afterwards. A 3:1 revenue ratio at weak margins is a different proposition from a 3:1 contribution ratio. A forecast over five years is different from observed twelve-month performance.

A very high ratio can indicate valuable customers, conservative spending, incomplete acquisition costs or an optimistic lifetime forecast. A lower ratio may support a sound business if payback is quick and enough contribution remains. Neither result diagnoses the cause by itself.

Compare the calculation with your own economics before comparing it with somebody else’s benchmark. Our advertising profitability guide explains the first-order cost definitions that underpin this longer-term view.

The next customer may cost more than the average

Blended CAC combines customers arriving through different routes. Some may have bought without the extra advertising. Platform-attributed sales can overlap, and matching a transaction to an ad does not prove the ad caused it.

When increasing spend, examine the additional investment and the additional outcome. Use a credible controlled experiment where volume and operations permit it. Otherwise compare cautious increments, record other changes and treat the result as an estimate rather than proof.

Watch the new cohort’s product mix, first-order contribution and early repeat behaviour. A larger budget can reach different customers, so the historic average may be an unreliable forecast for the next tranche.

Build a decision you can review

1. Rebuild one mature cohort. Include non-repeat buyers, net revenue and the costs required to serve them.
2. Reconcile acquisition costs. Separate paid-media CAC from the complete cost and document shared-cost allocations.
3. Set both ceilings. Specify retained contribution, an affordable payback window and a downside case.
4. Test the next increment. Review new-customer quality and the cash schedule before committing more.

Use the result in your marketing budget allocation. The useful output is an acquisition limit with a period, assumptions and a review trigger, not a ratio detached from a decision.