Understanding why customers leave — and how fast — is one of the most important measurements in any subscription or recurring-revenue business. A churn rate calculator translates raw headcount or revenue figures into actionable rates and lifetime-value estimates, so you can set realistic retention targets, model the impact of improving retention by even one percentage point, and compare results across different measurement periods without manual conversion.
This tool covers three complementary approaches in a single page: a customer churn mode for headcount-based analysis, a revenue churn (MRR) mode that handles expansion revenue and computes LTV directly, and a cohort analysis mode where you paste a real retention curve and the calculator derives the average lifetime and cumulative revenue per initial customer from the data itself.
How it works
Customer churn mode
The period churn rate is simply the number of customers lost divided by the number of customers at the start of the period:
Churn rate = customers lost / customers at start
Because you might measure quarterly or annually rather than monthly, the calculator normalises to a monthly equivalent using the compound-rate formula:
Monthly churn = 1 - (1 - period churn)^(1 / period months)
Annual churn is then derived as the complement of surviving 12 consecutive months:
Annual churn = 1 - (1 - monthly churn)^12
The average customer lifetime follows directly: if you lose a constant fraction of customers each month, the expected number of months before a random customer churns is the reciprocal of the monthly churn rate — so a 5% monthly churn implies an average lifetime of 20 months.
Revenue churn (MRR) mode
For subscription businesses the revenue-weighted view is often more important than the headcount view. Gross MRR churn measures the fraction of recurring revenue lost to cancellations and downgrades:
MRR churn rate = MRR lost / MRR at start
Net MRR churn subtracts expansion revenue — upsells and cross-sells from existing customers — from the loss figure. When expansion exceeds losses, net churn is negative, which is sometimes called “negative churn” and is a very strong growth signal.
Net MRR churn = (MRR lost - MRR expansion) / MRR at start
LTV is calculated as ARPU multiplied by the gross margin fraction divided by the monthly churn rate:
LTV = ARPU x (gross margin / 100) / monthly churn
Cohort analysis mode
Rather than assuming a constant churn rate, cohort analysis uses an observed retention curve — the percentage of a starting cohort still active at each monthly interval. The average customer lifetime is estimated as the area under the retention curve using the trapezoidal rule. LTV is then the cumulative gross margin earned per initial customer summed across all intervals.
Worked example
A SaaS product starts January with 2,000 customers and loses 120 over the month.
- Monthly churn rate: 120 / 2,000 = 6.0%
- Monthly retention: 94.0%
- Annual churn (implied): 1 - 0.94^12 = 52.3%
- Average lifetime: 1 / 0.06 = 16.7 months
With ARPU of $80/month and a 70% gross margin, the LTV is:
$80 x 0.70 / 0.06 = $933
Reducing monthly churn from 6% to 4% raises average lifetime to 25 months and LTV to $1,400 — a 50% increase in customer value from a 2 percentage-point retention improvement.
Formula note
The monthly normalisation formula — 1 - (1 - r)^(1/n) — is the geometric equivalent of dividing by n. It is correct because churn compounds: if 14.3% of customers leave each quarter, roughly 5% leave each month, not 4.77% (14.3/3). Dividing by the number of periods is a common mistake that overstates retention. Always use the geometric formula when converting between periods.