A suite of standards (from the RICS, the Royal Institution of Chartered Surveyors) that define exactly how to measure and cost construction work consistently, across three volumes covering cost planning, detailed measurement, and maintenance costs. NRM is the rulebook that makes QTO and 5D meaningful in practice - it defines what actually counts as "one unit" of a wall, a door, or an excavation, so quantities extracted from a BIM model can be compared and costed consistently between projects and quantity surveyors.

Without a measurement standard like NRM behind it, a model-derived quantity takeoff is just a number - NRM is what makes it a trustworthy one.