SaaS customer lifetime value: the churn-based calculation

Aug 18
3 min read

Updated: 4 days ago

Introduction

Lifetime value in a subscription business is calculated differently from a retail one, because there is no fixed number of purchases. The customer keeps paying until they stop, so the calculation runs on churn rather than on purchase frequency.

That makes it more elegant and considerably easier to get wrong.

The general concept is covered in how to calculate customer lifetime value; this is the subscription version.

1. Calculating SaaS customer lifetime value

The standard form:

LTV = (average revenue per account × gross margin) ÷ customer churn rate

With $80 monthly revenue per account, an 80% gross margin, and 2% monthly churn:

($80 × 0.80) ÷ 0.02 = $3,200

The margin term is not optional. Software margins are high but not total — hosting, support and payment processing are real — and using revenue instead inflates the figure by whatever your cost of service is.

2. Churn is doing all the work

Notice how sensitive the result is. At 2% monthly churn, lifetime value is $3,200. At 4%, it halves to $1,600. At 1%, it doubles.

This is why churn matters more than almost anything else in a subscription business, and why small retention improvements produce disproportionate changes in what you can afford to spend acquiring customers.

It also means an optimistic churn estimate will justify spending that will not be recovered.

3. Use a churn figure you can defend

The most common error is calculating churn over too short a period, or from too small a base, and treating the result as stable.

Use a full period with enough customers that a couple of departures do not swing the figure. If your business is young, use a conservative estimate rather than your best month — the cost of being wrong here is spending real money against imaginary revenue.

Where cohorts differ markedly, calculate separately rather than blending.

4. Add expansion revenue carefully

If customers upgrade over time, lifetime value is higher than the basic formula suggests, and the adjustment can be substantial.

The cleaner approach is net revenue retention: revenue retained from a cohort including upgrades and downgrades, divided by what it started at. Above 100% means expansion outpaces churn, and lifetime value grows over time rather than being fixed.

Include expansion only if you can evidence it from actual cohort behaviour. Assuming it is the fastest route to an unaffordable acquisition budget.

5. Segment by plan and by acquisition channel

A blended figure across self-serve and sales-led customers describes neither.

Self-serve customers typically pay less and churn faster. Sales-led customers pay more and stay longer. The average matches no actual customer and can conceal one motion subsidising the other.

Segment by plan tier and by channel, and calculate lifetime value for each. Then compare each against its own acquisition cost.

6. Pair it with payback period, always

Lifetime value tells you whether a customer is worth acquiring. Payback period tells you whether you can afford to acquire them now.

Payback = acquisition cost ÷ monthly gross profit per customer

Two businesses with identical lifetime value can be in very different positions if one recovers its acquisition cost in three months and the other in eighteen. The second needs far more cash to grow at the same rate.

7. Recalculate quarterly

Lifetime value moves whenever pricing, margin, churn or mix changes — which is constantly in a growing business.

Recalculate quarterly alongside churn and payback period, and use the conservative version for planning. A figure that is optimistic and eight months old is the most expensive number in a subscription business.

Conclusion

Calculate lifetime value as margin-adjusted revenue divided by churn, and recognise that churn dominates the result.

Use a defensible churn figure, add expansion revenue only from evidenced cohort behaviour, segment by plan and channel, and always pair the figure with payback period. Then recalculate quarterly and plan with the conservative version.