Tortoise growth in captivity depends completely upon how the tortoise is being kept-the temperatures, foods, lights, humidity levels (or lack of), etc... Different people keep them under different conditions. In an ideal captive situation an Eastern Hermann's should about double is birth size in one year. Many will grow larger due to their captive environment. Hermann's are very subject to accelerated growth in captivity so it is always desireable to allow them to grow at a slower, more normal rate.