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Churn and retention calculator

Turn customer counts and revenue into churn rate, retention rate, NRR and GRR.

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Churn and retention calculator
Paste your subscriber counts and this tool turns them into the metrics a subscription business tracks every period: customer churn rate, customer retention rate, net revenue retention (NRR) and gross revenue retention (GRR). Enter one line per period as period;start;churned;new;revenue — for example Jan;500;40;25;12000 — and it works out how many customers you ended with, what share of the starting base you kept, and how revenue moved with them. Add more lines to see the trend over time.
The period option labels rows as months, quarters or years, which sets how the churn rate is annualized or converted to a monthly equivalent — handy when a monthly figure needs restating in annual terms. Turning on "Account for revenue expansion and downgrades" stops NRR and GRR from simply mirroring customer retention: it estimates how much of each period's revenue came from new customers rather than the existing base, so upsells can push NRR above 100% while GRR stays capped there to isolate churn and downgrades. "Show average customer lifetime" adds an estimate — 1 divided by the latest churn rate — of how long a typical customer stays. Pick a currency for the revenue figures and text or a tab-separated table for the layout.
A line that doesn't split into exactly five semicolon-separated fields, or where churned customers outnumber the starting count, is flagged with the offending text quoted back. Windows and Unix line endings both work, and the live tally under the output always shows the latest period's churn and retention rate as you type.
Everything runs locally in your browser — customer counts and revenue never leave your device. Copy the result, download it as a .txt file, or send it back to the input to add another period.
FAQ
What do the five fields in each line mean?
period;start;churned;new;revenue — a label for the period, customers at the start, customers who churned, new customers gained, and total revenue for that period. The tool works out the ending customer count for you.
What's the difference between NRR and GRR?
Gross revenue retention (GRR) only counts losses — churn and downgrades — so it never exceeds 100%. Net revenue retention (NRR) also counts expansion revenue from existing customers, so it can go above 100% when upsells outweigh losses.
Why is NRR/GRR empty on the first period?
Both compare a period's revenue to the previous period's, so the first row in a list has no earlier revenue to measure against. Add a prior period, or read the customer churn and retention figures on their own.
How does the monthly-to-annual churn conversion work?
It compounds the period rate rather than simply multiplying by 12 or dividing by 12 — churn compounds the same way interest does, so a 5% monthly rate doesn't equal 60% a year.
Is my customer and revenue data uploaded anywhere?
No. Every calculation runs in your browser — the numbers you paste never leave your device.