You can back up an unlimited number of standard size photos and videos for free (standard size means that photos are 2048px or less on the longest edge and videos are less than 15 minutes long and have 1080p resolution or less). Auto Backup is set to back up at full size by default. Learn how to change your back up setting to standard or full size.
What counts against your free Google Drive storage quota?
If you have your back up setting set to full size, then photos larger than 2048px on the longest edge (full size photos can be no larger than 100 MB) and videos longer than 15 minutes or saved at a resolution higher than 1080p count against your free Google Drive storage quota. If you start approaching the free storage limit, you'll see a notification. If you run out of storage, we'll automatically switch to backing up at standard size. Learn more about Google Drive storage plans and pricing.