Churn Rate

Churn rate is the percentage of customers who discontinue using a product or service over a given period. The workbook says this metric is crucial to ensure that the investee company is in a sustainable business environment.

It is the other half of customer acquisition cost. A company can win customers efficiently and still go nowhere, because it loses them as fast as it buys them. Churn is what converts a growth story into a treadmill.

Churn sits in the workbook's revenue growth and customer retention group of start-up metrics, alongside monthly recurring revenue, annual recurring revenue, customer lifetime value, customer acquisition cost, daily and monthly active users, and net promoter score. They are read together, and churn is the hinge.

The arithmetic that makes it matter: the average life of a customer is the reciprocal of the churn rate for the period. At 4% monthly churn a customer stays roughly 25 months; at 2%, roughly 50. Since CLTV is average purchase value times average number of purchases, halving churn doubles the number of purchases, doubles CLTV, and doubles the CLTV/CAC ratio — without the company spending a rupee less on acquisition.

Which is why a venture investor will often pay more attention to a two-point move in churn than to a large move in revenue. Revenue can be bought. Retention has to be earned, and the workbook pairs churn with DAU/MAU, which measures how many unique users engage daily or monthly and so shows the customer's loyalty to the company, and with NPS, which asks whether they would recommend it.

Churn rate = Customers lost during the period
             / Customers at the start of the period

Average customer life (periods) = 1 / Churn rate

The period has to be stated — monthly and annual churn are not the same number.

Vaayu Software, a subscription business, is being appraised by a Category II AIF for a Rs 35 crore round.

Subscribers at the start of the month           20,000
Subscribers lost during the month                  800
Monthly churn   800 / 20,000                =     4.0%

Average customer life   1 / 0.04            =     25 months
Average revenue per subscriber per month        Rs 1,200
CLTV   1,200 x 25                           =  Rs 30,000
CAC                                            Rs  9,000
CLTV / CAC                                        3.3x
ARR    20,000 x 1,200 x 12                  =  Rs 28.8 crore

The company then fixes onboarding and support, and churn falls to 2%.

Average customer life   1 / 0.02            =     50 months
CLTV   1,200 x 50                           =  Rs 60,000
CLTV / CAC                                        6.7x

CLTV doubles and the ratio doubles, with CAC untouched at Rs 9,000 and not one extra rupee of marketing spend. On a base of 20,000 subscribers the company also stops losing 9,600 customers a year instead of 4,800 — at Rs 9,000 each to replace, that is Rs 4.32 crore a year of acquisition spend it no longer has to make just to stand still.

That Rs 4.32 crore is more than a tenth of the round being raised. It is the clearest illustration of why an investor treats churn as a valuation input and not a customer-service statistic.

Chapter 14 (Valuation), section 14.8.1, defines churn rate inside the list of metrics used for start-up valuation and performance assessment. The same list supplies MRR, ARR, CLTV, CAC, DAU/MAU, NPS and the viral coefficient, and questions typically ask you to match one definition to one metric, or to compute a percentage.

• Churn is always attached to a period. Monthly and annual churn are different numbers and cannot be compared directly.
• Customer churn and revenue churn diverge when the customers leaving are much larger or smaller than average.
• DAU/MAU measures engagement, not churn. It shows loyalty; it does not count departures.
• Churn changes CLTV without touching CAC, so it moves the CLTV/CAC ratio on its own.
• A low churn rate on a tiny base proves little — the workbook's point about metric lists is that they are read together, never in isolation.
• The reciprocal relationship — average life equals one divided by churn — is the step most often skipped in a CLTV computation.