The du command will calculate the size of a directory as a whole:

du

The 32 number here is a value expressed in bytes.

Running du * will calculate the size of each file individually:

You can set du to display values in MegaBytes using du -m, and GigaBytes using du -g.

The -h option will show a human-readable notation for sizes, adapting to the size:

Adding the -a option will print the size of each file in the directories, too:

A handy thing is to sort the directories by size:

du -h <directory> | sort -nr

and then piping to head to only get the first 10 results:

The du command works on Linux, macOS, WSL, and anywhere you have a UNIX environment