How big does a chicken coop need to be?

I'm expecting 15 pullets in two days. How big of a coop do I need? I intend to provide ample outside space as well.

In addition, I'm currently renting. I want to build my own coop to save money, but I also want it to be semi-mobile so that when we move we can take it with us. We'll be here for at least one more year, but who knows if any longer than that. Thoughts?

I'm new to chickens, so any tips are appreciated.

The standard rule is 4 square feet per bird. That means you will need 60 s.f. for 15 hens.

If you build it in panels, you can bolt them together (rather than nailing). When you get ready to move, just unbolt all of the panels.

It also depends on how you will manage them. I use an approximately 8'x9' coop for 25 birds, but they get moved around a lot and it's pretty much a bedroom only. The more time they will have to spend in there the bigger it should be, ideally. I would say to build it as big as you can manage/have space for, and still be able to break down and move reasonably easy. Check out Harvey Ussery's website/book for some good start up info if you are new to chickens, http://themodernhomestead.us/article/Poultry.html

We try for five square feet per hen - that works very well for us. For free instructions on how to build a low cost coop from recycled mat'l see the article here: http://urbanfoodfare.blogspot.com/2011/08/living-architecture-critter-proof-coop.html