How is plumbing pipe measured

Metric sizes are easier than imperial sizes. The sizes indicated in this system are the actual dimensions of the pipe or fittings. For example, 50mm pipe measures 50mm on the outer diameter. A 50mm socket will measure 50mm on the Inner Diameter.

A 50mm spigot fitting will measure 50mm on the outer diameter. Although we offer threaded fittings for 'Metric sizes' generally these fittings will be metric on the plain side spigot or socket and the thread will usually be Imperial BSP B ritish S tandard P ipe.

Keep in mind that pipe size refers to a nominal - not actual - inside pipe diameter. Schedule refers to the pipe's wall thickness. The actual physical OD is larger than it's nominal OD. The dimensions provided for tubing on the other hand refer to the actual outside diameter.

In other words, the actual physical OD of a tube is just the same as it's nominal OD. For sizes larger than inch, NPS corresponds to the actual outside diameter. For each nominal pipe size, the outside diameter O. The wall thickness of tubing is measured in inches.

You can see by the chart at the right, not all 12 Gauge allows a thickness between 0. The typical value, which is not half way between, is used for calculation of section properties.

When mass production of pipe began, there was a need for standardization. NPS is the North American standard today. Knowing the background on how and why the sizing is determined is critical, though you will not necessarily need to resort to advanced math to figure it out.