TreeSize, as its name indicates, will show the size of the folders in a tree structure from its own interface, even though it also allows the possibility to access the information that it provides from the Windows Explorer contextual menu if you install the pertinent option. A size bar beside each folder name will represent its size visually.
You can see the size of each folder in different measures and even using percentages. When you download TreeSize free you will also have the possibility to see the NTFS compression ratio, a tool that has now been included here after another program by the same developers, NTFSRatio, was discontinued.
Find out the size that the folders occupy on your hard drive when you download TreeSize free on your computer. View the information about different modes, order the results as you like most and organize all your hard drive so as to make sure that you don't run out of free space.