Age of an African Spur-Thighed Tortoise by: Shelly
If you are not around when your tortoise hatches, the only way to tell its age is by the size of its shell.
An African spur-thighed tortoise will be about 2-3 inches long when it hatches and will grow to be about 7 inches long. It will reach about 10 inches rather quickly if it is healthy. It will finally grow to about 18 inches, although some will get to be up to 36 inches long. As you can see, there is a wide variation, so even the size of the shell doesn't help all that much.
Once a tortoise is full grown, there is no reliable way to tell its true age.
The only really reliable way to know the age of a tortoise is to be there when it hatches.