Calculate Customer Churn Rate

Excel & Google Sheets

How it works

Churn is the customers you lost during the period divided by the customers you started with. Losing 25 of 500 customers is 25/500 = 0.05 — a 5% monthly churn rate. The denominator matters: dividing by the period's starting count keeps the rate honest, because new customers signed this month haven't had a chance to churn yet. Retention is simply the complement — =1-B2/A2 gives 0.95, and churn plus retention always equals 100%, a quick sanity check on any dashboard. Format both as percentages.

B2

Customers lost during the period — cancellations, non-renewals.

/A2

Divided by customers at the START of the period, not the end.

=1-B2/A2

Retention rate: the share you kept. Churn and retention sum to 100%.

When to use it

Use it for monthly SaaS subscriber tracking, membership and newsletter cancellations, or comparing churn across plans and cohorts to see where customers leak out.

Common mistakes

• ✕Dividing by the end-of-period customer count.

  ✓New signups inflate the denominator and hide real churn. Divide by the starting count: =B2/A2 with A2 = customers on day one of the period.

• ✕Comparing monthly churn against annual churn.

  ✓5% monthly compounds to about 46% per year — not 5%. Keep every row on the same period length before comparing or charting.

• ✕Counting customers who both joined and left this month inconsistently.

  ✓Pick a rule — many teams exclude same-month joiners from both numbers — and apply it every month, or the trend line is noise.