Back when i was using xp i had this program called Folder Sizes
that showed the folder(also file) size in the explorer column
I was wondering will that option be or is available in nautilus or other file-manager
Screenshot
There are several ways to do this. (Disclaimer: all this methods can only make the folders show the amount of items that they contain, not their actual size)
Probabliy the most used option is to use the "List View" mode. You can enable it by going to View menu and click on List. You get this:
But there's also a really comfortable method to do it, which allows you to navigate your folders using the "Icons View". All you have to do is going to Edit menu, click on Preferences option and then click on the Display tab. After that you have to set the first zooming option to show you the size of your folders and files.
