What Does Nominal Pipe Size (NPS) Mean?
Nominal pipe size (NPS) is a set of standard North American sizes to designate pipe diameter and thickness for pipes that are used for low and high pressures and temperatures. Nominal means something that is not specified, and in terms of pipe sizes, it refers to the diameter of the pipe hole with a dimensionless number.
NPS is used for calculating the required pipe strength and outer diameter (OD) required for installing pipelines using trenchless methods since these methods require pulling the pipes through boreholes.