Determining The Complete Size Of A Folder & Its Sub-Folders in Finder?
In Finder:


Either:


Option + click a folder.
Or: Click the gear icon in the header.
Or: Select the View menu, and then "Show View Options".
Or: Command + J

Select "Show View Options"
In the 4th subset of options select the box "Calculate all sizes".


If a folder is empty it will only show "--" like all the folders previously did.