NRR measures how much revenue you keep and grow from existing customers over a period — after accounting for expansion (upsells, seat adds), contraction (downgrades), and churn. A 110% NRR means your existing customer base paid 10% more this period than last, even after all losses.
NRR above 100% is the holy grail of SaaS: growth without acquiring a single new customer. It is the primary metric investors use to distinguish a leaky bucket from a compounding flywheel. Best-in-class B2B SaaS typically runs 115–130% NRR. Below 90% is a retention crisis.