Diameters in DN or in NPS

From within the industrial market we find these two systems to size the diameters for pipes, tubes, valve connections and other devices:

• Nominal pipe size (NPS) , defined by the American standard ANSI / ASME is based on inches .
• Nominal diameter (DN) , defined by the European standard ISO 6708 is based on millimeters .

We know that to determine the conversion operation from one value to another, we should only perform a simple simple mathematical formula (the value of a inch is 25.4 millimeters and that of 1 millimeter 0.0393701 inches); however we could not apply it to determine these values ​​because each system uses a commercial measure that does not correspond with the real value of the outside diameter of the pipe but with the inside of it. We observe a difference of 0.4 millimeters in the value DN 25 while in larger sizes the difference is even greater , for example: 120 inches is actually 3048 millimeters, 48 ​​millimeters more than the DN 3000 value.

In order to make things easier for you, you have above a conversion table so that you can determine the equivalent value of each measure .