In the command line type the following command within the desired directory

{codecitation class=“brush: bash;"}du -c{/codecitation} This will give you the usage/size of all the folders within that particular directory. 

du =  estimate file space usage -c = total

To get the size/usage in a Human readable format eg. Megabytes/Gigabites append the -h option to the command above.

Example below:

{codecitation class=“brush: bash;"}du -ch{/codecitation}