Usually by eight weeks or so you should have a pretty good idea, some boys will be obvious a lot sooner, some later... if you have any you are questioning (or just to feel safe) you can post pictures on the What Breed/Gender is this forum for opinions www.backyardchickens.com/f/15/what-breed-or-gender-is-this there is also an article in the Learning Center that covers some of the differences you might see at different ages https://www.backyardchickens.com/a/is-my-chicken-a-pullet-hen-or-a-cockerel-cock
