How fast do red footed tortoises grow in captivity?

They hatch out at around 2 1/2 inches and are usually around 4 inches at a year old. By 2 years of age mine are generally 5 to 6 inches. These measurements are the SCL (straight carpace length ). They continue to add about 1.5 inches a year until full grown. My adults range from 12 to 14 inches.