Searching for app sizes
You can find it by searching for relevant terms

The final RTM (released to manufacturing) version of Windows 8 is very similar to the Windows 8 Release Preview that was launched to the public at the end of May. However, there are some new features in the RTM version of Windows 8 that is not in the Release Preview. Today, I want to talk about a new neat little handy feature that is included in the RTM version of Windows 8. It is a new addition to the Metro Style control panel in Windows 8 that will let you see how much space is left on your hard drive AND how much each metro style app is occupying in your hard drive. I am sure many of you will find this feature a very welcoming one, as in the past, it was quite hard to see how much disk space these apps were using without actually examining the app directories manually.

Show Windows 8 App Sizes
Windows 8 app sizes are shown under the General Settings tab of PC Settings.

To activate it, go to the General section of the Metro Style control panel. Or you can directly search for it from the start screen by typing relevant words like, “app size”, “size”, “space”, “disk space”, etc. You will need the RTM version of Windows 8 (or later) to be able to do this!