How to Accurately Measure Directory Sizes on Linux with du

Linux treats everything as a file, so the ls command reports a fixed 4 KB size for directories because that value represents the space used to store the directory's metadata, not the actual data contained within.

The du command (short for disk usage ) is a standard Unix tool that estimates the amount of space used by files and directories. Below are common usages illustrated with the example path /home/alvin/Documents.

Get the total size of a directory

$ du -hs /home/alvin/Documents
or
$ du -h --max-depth=0 /home/alvin/Documents/

20G    /home/alvin/Documents

-h

– display sizes in human‑readable units (K, M, G). -s – show only the summary total. --max-depth=N – limit recursion to N directory levels.

List each subdirectory’s size (including deeper levels)

$ du -h /home/alvin/Documents/ | sort -rh | head -20

20G    /home/alvin/Documents/
9.6G   /home/alvin/Documents/drive-alvin
6.3G   /home/alvin/Documents/Thanu_Photos
5.3G   /home/alvin/Documents/Thanu_Photos/Camera
... (remaining lines omitted for brevity)

Show size of every file and directory using a wildcard

$ du -hs /home/alvin/Documents/* | sort -rh | head -10

9.6G   /home/alvin/Documents/drive-alvin
6.3G   /home/alvin/Documents/Thanu_Photos
3.2G   /home/alvin/Documents/drive-mageshm
756K   /home/alvin/Documents/Bank_Details
272K   /home/alvin/Documents/user-friendly-zorin-os-15-has-been-released-TouchInterface1.png
... (remaining lines omitted)

Exclude subdirectories from the size calculation

$ du -hS /home/alvin/Documents/ | sort -rh | head -20

5.3G   /home/alvin/Documents/Thanu_Photos/Camera
5.3G   /home/alvin/Documents/drive-alvin/Thanu-videos
2.3G   /home/alvin/Documents/drive-alvin/Thanu-Photos
1.5G   /home/alvin/Documents/drive-mageshm
... (remaining lines omitted)

Show sizes of first‑level subdirectories only

$ du -h --max-depth=1 /home/alvin/Documents/

3.2G   /home/alvin/Documents/drive-mageshm
4.0K   /home/alvin/Documents/alvin
756K   /home/alvin/Documents/Bank_Details
9.6G   /home/alvin/Documents/drive-alvin
6.3G   /home/alvin/Documents/Thanu_Photos
20G    /home/alvin/Documents/

Get a cumulative total with statistics

$ du -hsc /home/alvin/Documents/* | sort -rh | head -10

20G    total
9.6G   /home/alvin/Documents/drive-alvin
6.3G   /home/alvin/Documents/Thanu_Photos
3.2G   /home/alvin/Documents/drive-mageshm
756K   /home/alvin/Documents/Bank_Details
... (remaining lines omitted)

These examples demonstrate how different du options ( -h, -s, --max-depth, -S, -c) can be combined with sorting and filtering utilities to obtain precise disk‑usage information for any directory hierarchy.