Part of it depend on breed, and a bigger part depend on the individual hen.. I have had hens start lay at 5mth and Hens..especially the Rhodabarrs that I had, started lay around 7-8mths old. But most, like my Plymouth Rocks, RIRs Sussex, Australorps, Easter Egges and Sexlinks, have been between 5 to 6mths old. Again, When the Hens are Ready..