15mm X 1/2 inch connectors

[JayJay1978]

This is a question that has had a lot of debate on here with lots of different answers. I need to connect to 1/2 inch pipe at home to add a new radiator.

I know imperial pipe was measured on the inside and metric is measured on the outside.

Is 1/2 inch pipe bigger or smaller on the outside compared to 15mm?

 

[kevplumb]

same size just use 15mm no 1s

 

[JayJay1978]

I'm sure I could get a 15mm fitting on there but the endfeed 15mm x 1/2 inch convertors I bought clearly have the smaller end as the 1/2 but why do so many people say 1/2 has the bigger OD?

I'm confused??

 

[doitall]

Some old 1/2" pipe is larger. not certainly not the norm.