Hi, welcome to BYC!
I will give you the general guide lines... 4 square feet per bird in the coop and 10 square feet in the run. With about 1.25 feet roost space each Even if you plan to free range you should set up an enclosed run for when you need predator protection or to confine the girls and teach them to lay in the boxes. These are a minimum suggestion. Things like how often you clean and how bad your weather gets can effect these parameter. If they will spend a lot of time indoors, go bigger. And don't forget to allow space for feeders, waterer, and lay boxes... mine are all outside my coop measurement. But if you have things taking up floor space, it cuts room for the girls.
1 box for every 2-3 hens is usually good.
Do not buy those pre fab coops that say for 6 birds, they will quickly out grow it. Those way over estimate. Don't forget windows and roof ventilation.
Remember all your girl will molt and stop laying during winter # 2. So just in case you want to add more in that spring so you can still have eggs next winter.... I would build bigger than you think you need. Chicken math is dangerous!
It's best to have your coop done before you get your girls. But don't wait too late or they won't lay very soon. No later than April for me to get eggs around 4th of July.
If you haven't considered it... look into Mama Heating Pad to brood your babes and think about doing out of the house.
Chickens are a lot of fun. We watch chicken TV in our back yard for hours.