Tool

Which size is my pipe?

Measure the outside of the pipe and type it in. We tell you its size in each kind of pipe we stock, to within 1.2 mm.

Where to measure

1 Across the outside, with a caliper.

2 No caliper: a thread once round.

Measure across the outside of the pipe, not the hole. Close the caliper on the pipe and read it in millimetres.
No caliper? Wrap a thread once round, mark where it meets, measure the thread and divide by 3.14. Or pick “Round, with a thread” and we divide for you.

How did you measure?

Across, with a caliperRound, with a thread

Outside diameter (mm)

Across the outside of the pipe, not the hole.

Type what you measured, in millimetres. The size shows here and in the table below.

Outside diameter in mm. CPVC is made to copper-tube sizes, uPVC and GI to iron-pipe sizes, so a ¾″ CPVC pipe is about as wide as a ½″ uPVC or GI one.

Nominal pipe sizes with the outside diameter of CPVC, uPVC and GI pipe, in millimetres
Size	mm	CPVC outside diameter	uPVC outside diameter	GI outside diameter
½″	15	15.9	21.3	21.3
¾″	20	22.2	26.7	26.9
1″	25	28.6	33.4	33.7
1¼″	32	34.9	42.2	42.4
1½″	40	41.3	48.3	48.3
2″	50	54.0	60.3	60.3