Is there a way to see how how much space a label/folder is taking up on Gmail ?
I know I can see the overall account info at the bottom i.e., "x of 15gb" - but is there a way to break this down by folder or label?
This is currently not possible with GMail web interface. As a workaround I would suggest using any IMAP client.
Why not simply do the following:
You should be able to do a search, and download an archive with your past search. A lengthy process but will let you know at the end.
You could also go into settings/labels and view how many conversations are saved under each label.