Mac OS X users can quickly find out the total space occupied by folders and files using the status bar. For example, in the below screenshot the home folder contains 15 items and the total size of all the items is 172.18 GB.
Show status bar on Mac
If the status bar is not shown on the Finder window then you can turn on the status bar using View option. Click View menu on Finder window and select Show Status Bar from the list.
If the finder window does not show toolbar then the status bar would be displayed at the top of the finder window.