--du For each directory report its size as the accumulation of sizes of all its files and sub-directories (and
their files, and so on). The total amount of used space is also given in the final report (like the 'du -c'
command.) This option requires tree to read the entire directory tree before emitting it, see BUGS AND NOTES
below. Implies -s.
Adding on the accepted answer... with any substantial number of folders, you are going to potentially get a huge output from that command.
If like me, you are wanting to identify some big folders to purge because you are filling up your drive, you might find it helpful to combine the tree command with a grep to limit it to folders that are Gigabytes in size, saving yourself the need to traipse through the whole output: