Expansion MRR tracks the incremental MRR gained from current customers in a given month, driven by plan upgrades, add-ons, or increased usage. It is a core component of calculating NRR and indicates the strength of land-and-expand motions.

Example: In March, 15 existing customers upgrade their plans or add seats, contributing a combined $8,500 in new MRR. This $8,500 is the Expansion MRR for March.