I need to be able to see the tail. Can you get another pic? Have someone hold the tortoise against their torso with its head pointing toward the sky and get in there and get a close up of the tail.
Like this:
You can usually tell when they are 14-16" long. Yours is looking male to me since the whole anal scute opening looks like it is filled with tail, but I'll reserve judgment until I see a better pic.