Answer
Jan 27, 2026 - 10:15 AM
BSP (British Standard Pipe) can refer to both ID (internal diameter) and OD (outside diameter), but standard BSP pipe sizes are typically named by their approximate internal diameter (ID). However, the actual measured size of BSP threads refers to the outside diameter (OD) of the pipe's threads. So, BSP pipe size names are based on ID, while thread measurements use OD.
