To establish how many chickens you will need is to look at how many eggs you use on average in a week. From there you can then decide how many chickens you will need to provide you with that number. A good laying hen will lay about 5 eggs a week. So, if you have 2 chickens you will get 10 eggs a week, or thereabouts, 4 chickens, 20 eggs and so on. Layers start laying eggs at about 6 months of age and will be very good layers for at least 2 years after that. However, as they get older they become less productive.