How to get the size of a directory using the command line in Linux

Open a new Terminal Window and type the following command:

du -shc folderPath

Explanation of the du command:

du - estimate file space usage

-s, --summarize, display only a total for each argument
-h, --human-readable, print sizes in human readable format (e.g., 1K 234M 2G)
-c, --total, produce a grand total

Replace folderPath with the folder to check the size on.