Google grants us all unlimited storage of Google Docs on Google Drive, but only a limited amount of space for other file formats. Because of this, it makes sense to convert other formats to Google Docs if possible.
How-To Geek reminds us of this option:
If you have documents in Microsoft Office or OpenOffice format, you can convert them to Google Docs files to save space. To do so, simply right-click the document in your Google Drive, point to Open with, and select the Google Docs application. Google Docs will create a new copy of that file in Google Docs format, allowing you to erase the original file.
You can also enable the "Convert uploaded files to Google Docs format" option in the upload dialog to have new documents automatically converted. Note that you may lose some advanced formatting if you do this.
If you've been using Google Drive to store Microsoft Office or Open Office files that could be converted to Google Docs, you can free up that space with a simple file conversion.
Check out more Google storage-saving ideas at the link below.