Google Drive and OneDrive have different storage sizes because they calculate storage usage quite differently.

Here are some differences:

  • Google Drive counts files in the trash against your storage quota.
  • Google Drive counts versions of files against your storage quota (i.e., if a file is changed twice then it will use double of quota than a file that was changed just once).
  • Google Drive does not count files which are in Google Docs format against your storage quota.
  • MS Office files in Google Drive take their full size while OneDrive will store these files in MS Office format and compress them (so they will use a fraction of the storage space than on Google Drive).
  • OneDrive de-duplicates some files so they take less space in OneDrive. When downloaded, the files are of their correct size. For example, if you have two PDF files in a OneDrive folder and they have exactly the same content, they will use storage on one file.
  • OneDrive will not upload temporary files (i.e., files that start with ~$).

More about how Google Drive calculates storage quota can be found here: