Paying Accounts
The count of customers actually paying you — the simplest measure of how big your base really is.
What is it?
Paying Accounts is the number of accounts with MRR greater than zero at a point in time. Free-plan and trial accounts do not count — only customers actually paying you. If 80 of your 200 accounts are on a paid plan, your paying-accounts count is 80.
It is the plainest measure of base size, and the denominator behind several other metrics. Total MRR divided by paying accounts gives ARPA; churned accounts over paying accounts gives customer churn rate. Get this count wrong and both of those inherit the error.
How to calculate?
Count every account whose MRR is above zero during the period, and exclude anyone on a free plan or lapsed trial. The subtlety is timing — a point-in-time snapshot answers a different question than an average over the period, so decide which you mean and report it consistently.
Track paying accounts next to its movements — new, churned and reactivated logos — to see whether a flat count hides a base that is churning as fast as it acquires. A steady total can still mask heavy turnover underneath.