Image Credit: Cult of Mac
Our buddies at Cult of Mac have this great tip to share:
If you have a lot of pictures saved on your iOS device, you may want to know how much space those are taking up.
Go into: Settings>General>Usage
This will show you all the apps on your iOS device. From there, you can check out how much space your photos and videos are taking up on the device. It also shows how much space other apps are consuming. If you tap on the Photos & Camera tab, you will see how much space is being taken up by those photos and video.
As for me, I like to back up onto Dropbox. Occasionally, I will copy all photos over to a separate hard drive as well, and delete everything off the phone. This makes more room, of course.
Kudos to Cult of Mac for the tip