Google drive while a great service lacks the capability of showing the folder/file sizes. I guess it helps a lot to know the hogs, given you get only 15GB for free. I have been looking around for solution to this problem recently and found some discussion on Google Product Forum.
To cut the chase: you can browse to this link: https://drive.google.com/drive/quota and it should list the the files sorted by size. Well it is still missing the folder size information, but I feel better using this than some third party plugins.
