By default, OSX Finder does not show the size of folders. This is a bit of a pain when you want to know the size of an entire folder. Of course you can open the folder, highlight all the contents, and hit CMD-I, but this is kind of a nuisance. Also, I don’t even know if it includes the sizes of subfolders.
OSX Daily posted an article that explains how to do it.
nn> n> n n> * First, make sure to select list view from a Finder windown> n n> * Now open “View Options” from the View menu (or hit Command+J)n> n n> * Select the checkbox next to “Calculate all sizes”n> nn
The negative impact of enabling this option is that Finder may be a little slower/less responsive to use, since it now needs to calculate and update the file sizes for all folders. However, I doubt this will be a major issue. I think the benefit of seeing folder sizes in List view outweighs the performance hit. Of course, if you experience an inconvenient performance hit, you can disable this option.