Plumbing pipe threads and dimensions

BSP thread form stands for British Standard Pipe and is common in Australia and New Zealand. It is based on water flow trade size rather than actual diameter which can lead to some confusion when measuring ports. 

There are two types of BSP threads;
– BSPP – Female & male thread are both parallel
– BSPT – Female thread is parallel and the male thread is tapered.

Both threads have the same pitch, angle (55 degrees) and shape (rounded peaks and valleys).

The below table gives the major and minor diameter for each BSP Trade Thread Size. The minor diameter may be ever so slightly smaller than what is in the table depending upon where it has been manufactured to in the thread gauge.