BES Ltd., British Standard Pipe Thread Identification Chart.
BSP – This is an abbreviation used for British Standard Pipe threads, and the size refers to the nominal bore (or internal diameter) of the steel pipe the thread was originally designed for, not the diameter of the actual thread. Please measure your maximum (or major) thread diameter in millimetres and use the chart below to identify the BSP size you need.
Further advice can be obtained from our Technical Team if you are still unsure.
BSP Size
Actual Diameter of Thread
1/8"
9.728 mm
1/4"
13.157 mm
3/8"
16.662 mm
1/2"
20.995 mm
3/4"
26.441 mm
1"
33.249 mm
1 1/4"
41.910 mm
1 1/2"
47.803 mm
2"
59.614 mm
2 1/2"
75.184 mm
3"
87.884 mm
The information above is provided for guidance only. The data shown represents extracts interpreted by us of the British Standards. If more clarification and accuracy is required, you should refer to the relevant British Standard.
