Some of your readers have new, young Hermann’s tortoises and are wondering how big they’re gonna get. This is a more complex question than it seems, as there are several subspecies of Hermann’s tortoises and they differ considerably in size.
The main two subspecies are the eastern subspecies, Testudo hermanni boettgeri, and the western Testudo hermanni hermanni. Of the two, the eastern is considerably bigger, growing to about 11 inches (28cm) in carapace length and 6-9lb (3-4kg) in weight. The western ones, on the other hands, only get to be about 7.5 inches (18cm), but can be much smaller.
The situation is further complicated by the fact that there are other subspecies, including the Balkan Testudo hermanni hercegovinensis. This is comparable in size to the eastern subspecies. Furthermore, the subspecies are interbred now, especially in the pet industry, so it’s not always clear which species your dealing with, which might make the size of your individual tortoise a bit of a wild card.
In all subspecies, the female is slightly larger, maybe 10% larger.