How to estimate subscription lifetime value responsibly

Define value as contribution

Revenue lifetime value ignores the costs of serving the customer. For planning, multiply monthly revenue per customer by an explicitly defined contribution margin. At 50 monthly revenue and 60% contribution margin, each active customer produces 30 monthly contribution before acquisition and fixed overhead.

Use the churn formula with its assumptions

With constant monthly customer churn of 5%, a simplified expected lifetime is 1 / 0.05 = 20 months. Contribution LTV is 30 / 0.05 = 600. The model assumes one contribution before the first possible churn, constant monthly economics, no expansion and no discounting of future money.

Understand why the estimate is sensitive

If monthly churn rises from 5% to 10%, the same monthly contribution gives 300 LTV rather than 600. If churn falls to 2%, the estimate rises to 1,500. Those are arithmetic scenarios, not evidence that retention will stay constant. Zero observed churn in a small sample does not establish an infinite lifetime.

Use consistent churn definitions

Customer churn counts customers leaving. Revenue churn measures lost recurring revenue and can differ when large customers behave differently. Do not insert annual churn into a monthly formula. Cohort age, contract renewals and changing customer mix can make a single aggregate churn rate misleading.

Validate with cohorts before committing spend

Compare the estimate with cumulative realized contribution from groups acquired at the same time. Track acquisition cost separately; a 600 contribution LTV with 100 CAC leaves 500 before fixed costs and other excluded items in this simplified estimate. Timing and uncertainty still matter even when the ratio looks attractive.

Understand the series behind the shortcut

The 600 result comes from adding expected monthly contribution: 30 now, then 30 × 0.95, then 30 × 0.95², and so on. This geometric series sums to 30 / 0.05 when the assumptions remain constant indefinitely. It is not a claim that every customer stays exactly twenty months.

A finite twelve-month view gives about 275.78 of expected contribution: 30 × (1 − 0.95¹²) / 0.05. That is much lower than the indefinite total and helps reveal how much of the estimate depends on distant future retention.

Compare customers at the same age

A cohort acquired twelve months ago has had more time to generate contribution than one acquired last month. Compare their cumulative results at matching ages, such as month three or month six, rather than comparing lifetime totals observed over different durations.

Track service costs as well as revenue. A higher-paying customer may also need more support or infrastructure. If the cost to serve grows with customer age or usage, a constant margin may overstate the contribution that later months actually deliver.

Use a range when evidence is thin

Keep the 5% churn scenario as one estimate and calculate alternatives at 10% and 2%. The range from 300 to 1,500 illustrates model sensitivity; it is not a statistical confidence interval. A short observation period cannot establish which long-term assumption is most likely.

For acquisition decisions, pair LTV with realized cohort contribution, CAC and available cash. Avoid treating a particular LTV-to-CAC ratio as a universal approval rule. This model excludes fixed costs, discounting and risk, so a favourable ratio alone does not establish a sustainable business.

Try the numbers yourself

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