Size Table of Nominal Diameter (DN) vs. NPS (Inches)

In the valve industry, two common systems are used to define sizes:

• DN (Diamètre Nominal) – the metric standard, primarily used in Europe and Asia.
• NPS (Nominal Pipe Size) – the imperial system used mainly in North America.

Understanding the relationship between DN and inches (NPS) is essential for engineers, procurement teams, and installers when specifying valves, pipes, and fittings for international projects.

Below is a DN to Inches Conversion Table to help you quickly reference the equivalent nominal pipe size between these two systems.

What is DN?

DN (Diamètre Nominal or Nominal Diameter) is a standardized metric designation used to describe the size of pipe or valve bore. It does not directly represent an exact inner or outer diameter but rather a general size for identification.

What is NPS (Inches)?

NPS (Nominal Pipe Size) is an imperial-based system that describes the approximate inner diameter of a pipe in inches. It is typically used in the ASME/ANSI standard systems.

Note:

While DN and NPS values correspond closely in many ranges, they are not technically interchangeable measurements. Always verify with our sales team or standards when making critical decisions.

When to Use DN or NPS?

• Use DN when working with DIN, ISO, or EN standard pipelines and fittings (commonly used in Europe, Asia, and international markets).
• Use NPS (inch) when working with ASME, ANSI, or ASTM standard systems (commonly used in the U.S., Canada, and Latin America).

Conclusion

Having a quick reference for DN to inches conversions is essential for selecting the right pipe or ball valve size. Use this table to simplify your purchasing, design, or installation process across international projects.