How to calculate the thread size of a MALE BSP fitting/hose.

3/8 BSP Male plug

To first find the thread size you must.

1) Measure the outside diameter (O.D) of the BSP thread.

2) Take the O.D measurement in 16th of an inch and subtract 4/16" or quarter of an inch.

For Example

A BSP O.D male thread measure's 10/16" across minus the 4/16" allowance and it equals 6/16" or a 3/8" thread size.