Check online, ususally it's very easy to find, but for example to show all folder sizes and sort by size:
find . -maxdepth 1 -mindepth 1 -type d -exec du -hs {} \;
Obviously you run this in the root folder you want to analyse. Can be your main drive, but will take some time. Play around with the maxdepth and mindepth to get what you want.
But you get the gist. You can find commands to do loads of things with files and folders, it's a matter of googling only, and doesn't require installing or paying for any extra software.
Possible Duplicate: How do I get the size of a Linux or Mac OS X directory from the command-line? I am in a folder, and I want a list of all the sub-directories and their total sizes. I dont' ...
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