Formula
Total MRR / Total paying accounts
How to measure
Divide total MRR by the number of distinct paying accounts, treating multi-seat accounts as a single account.
Why track it
ARPA reflects the true billing unit in B2B and is more actionable than per-user metrics when accounts, not individuals, make purchase decisions.
Example
A company with $150,000 MRR across 300 accounts reports $500 ARPA.