This SAE Recommended Practice defines a set of measurements and standard procedures for motor vehicle dimensions. The dimensions are primarily intended to measure the design intent of a vehicle within a design environment (i.e., CAD). All dimensions in this practice can be measured this way.

In addition, some dimensions can be taken in an actual vehicle. If measurements are taken on physical properties, some differences in values should be expected. Also, care should be taken to not confuse design intent measurements with those taken on a physical property. It is intended that the dimensions and procedures described in this practice be generic in their application to both the HPM, described in SAE J826, and the HPM-II, described in SAE J4002. In some circumstances, the figures may only reflect one or the other.

Unless otherwise specified, all dimensions are measured normal to the three-dimensional reference system (see SAE J182), except ground-related dimensions, which are defined normal to ground. All dimensions are taken with the vehicle at curb weight unless otherwise specified. All dimensions are measured on the base vehicle and do not include Regular Production Options (RPO) or accessory parts, unless otherwise specified.

Although many terms and dimensions use human body parts in their name, they should not be construed as measures that indicate occupant accommodation, capabilities, or comfort.