NPS (Nominal Pipe Size)

Nominal Pipe Size (NPS) is a standardized measurement used to identify the approximate diameter of pipes, primarily in the United States. It indicates the pipe’s internal diameter, which influences flow capacity and compatibility with fittings. NPS numbers are standardized but don’t always match the exact inner or outer diameters; instead, they serve as a consistent reference point for pipe sizes across different types and materials. For example, a 4-inch NPS pipe is designed to have a standardized size that helps ensure proper fitting and system design, regardless of variations in actual dimensions.