You can use du command to see the folder size in LINUX including subfolders.:
du -h # including subfolders (-h means human readable format in MB, GB or TB)
If you want to exclude subfolders, type:
du -h –max-depth=1
If you want to know a specific folders size (easy to remember) type:
du -sh /home/someforlder
Where -h stands for human-readable & -s is to summerize the results.