Is pipe diameter measured interior or exterior?

Question

E.g. on screwfix.com there is a pipe 100mm is that interior diameter or exterior diameter?

Answer 1

It is definetly the interiror, sorry no sources, couldnt find any but i help withh plumming in bathrooms so i have a little experience.

Answer 2

It's the inside diameter.

Answer 3

Pipe size is a nominal inside diameter

Look up pipe size chart on the Internet

Answer 4

It depends upon which type of pipe you buy.  If you are buying copper pipe, which is similar to copper tubing it is measured in outside diameter.  Most other pipes such as black iron galvanized steel, or PVC piping  measure the inside diameter.As a rule of thumb, the difference between inside diameter and outside diameter is about an eighth of an inch. So half inch copper pipe is the same size as 3/8s inch black iron pipe.  

If you are installing sewer pipe you have to be careful because the vent piping is a different thickness than the drain piping so the connector you use for the drains will not fit on the vents even though both inside measurements are the same. The companies use the vent pipe rather than just the drain piping is because it is less expensive.

Answer 5

Pipe diameter is measured on the inside, Tubing for fluids is measured on the outside, electrical metallic tubing and conduits are measured on the inside.

Answer 6

Plumbing is I.D. (inside diameter) A/C and Refrigeration is O.D. (outside diameter)

Answer 7

Its is measured inside out. Or the opening size of the pipe.If they didn't do it that way you wouldn't have to buy reduces right.what your talking about is the thickness of the pipe or the gauge

Answer 8

No offense but that is a general search link. Most often Pipe is offered at an ID dimension,,,however wall thickness, exterior dimension might also matter.

Answer 9

Standard pipe is measured on the inside diameter, (ID) and tubing is on the outside diameter (OD).  Metric or SAE are measured the same.