A chicken is not considered a hen or rooster until it reaches one year of age. However, most breeds start to lay eggs around six months. Broilers can reach market size in as little as six weeks, so that could also be considered "full grown." Some breeds, such as Sumatras, and exhibition Orpingtons can take several years to fully mature (fully grown feathers and spurs, correct weight). I hope this helps! - BantamLover55
