Thread type: G (BSP) British Standard Pipe DIN ISO 228

Whitworth Pipe cylindrical Thread with sealant compound

A pipe thread is mainly used in plumbing, heating and air conditioning technology to connect pipes with fittings or valves. In Germany, the cylindrical Whitworth pipe thread is usually used as a pipe thread, which we would like to introduce to you in our table for the G pipe thread. This pipe thread is also known as BSP for British Standard Pipe and is standardized according to DIN ISO 228. It has a flank angle of 55° and as it is an imperial thread, the dimensions are given in inches.

The pipe thread G in the table is a cylindrical pipe thread. This means that both the external and internal threads are cylindrical and not conical, as is the case with some other types of pipe thread. As a result, the pipe thread does not seal in the thread, but must be used in combination with an additional sealant.

We have listed all sizes from 1/8 inch to 4 inch in the G pipe thread table. The thread designation is made up of the abbreviation G and an inch, which, however, does not correspond exactly to the outside diameter. When using the pipe thread G table, it is important to know that the outer diameter of a 1 inch pipe does not actually correspond to one inch (i.e. 25.4 mm). In fact, the outer diameter is 33.25 mm, as you can see from the pipe thread G table. The reason for this is the design of pipes at the time the pipe thread G was created. At that time, these required a significantly greater wall thickness.

The table for pipe thread G contains all the information you need to know to work with this type of thread. You can read off the outside diameter in inches and mm in the pipe thread G table. This means you don't have to convert if you prefer to work with one unit or the other. The pitch is also given in two ways in the pipe thread G table. One is in threads per inch, as is usual for inch threads. In addition, however, you will also find the pitch in mm, as you are used to with metric threads.

 Major Diameter
Major Diameter 
TPIPitch P in mm
G 1/8"0,3839,730280,907
G 1/4"0,51813,160191,337
G 3/8"0,65616,660191,337
G 1/2"0,82520,950141,814
G 5/8"0,90222,910141,814
G 3/4"1,04126,440141,814
G 7/8"1,18930,200141,814
G 1"1,30933,250112,309
G 1 1/8"1,49237,900112,309
G 1 1/4"1,65041,910112,309
G 1 3/8"1,74544,320112,309
G 1 1/2"1,88247,800112,309
G 1 3/4"2,11653,740112,309
G 2"2,34759,610112,309
G 2 1/4"2,58765,710112,309
G 2 1/2"2,96075,180112,309
G 2 3/4"3,21081,530112,309
G 3"3,46087,880112,309
G 3 1/4"3,70093,980112,309
G 3 1/2"3,950100,330112,309
G 3 3/4"4,200106,680112,309
G 4"4,450113,030112,309

Please note:
The Major Diameter of 1" Inch Pipe Thread is 33,25 mm or 1,309 Inches (not 25,4 mm)!
Historically it had it's origin from the manufacture of steel pipes in the beginning of the 20th century. In that time the normal 1" Inch pipes with the internal diameter of 1" Inch had a outside diameter of 1.309 Inches (about 33 mm).

Cross section of a G (BSP) thread