I don't know how to math. How many chickens can I have for a 4x4 coop; 4x6 run. They also free range everyday.
4x4 = 16 square feet = 4 chickens for the coop.
4x6 = 24 square feet = 2.4 chickens in the run.
4 chickens need 40 square feet in the run -- twice what you have. Expanding wider is better than a long, skinny run. If you can make it 6x8 or even 8x8 it would be more versatile and useful than 4x10 or 4x12.

If you start your own thread with photos of what you have (or what you're planning to build), we can better help you.
