!!! Lots of great peeps here! Make sure you check out the learning center!
As for your question, it really depends on the living conditions. Will they be free ranging in the day? What breeds will you be having? Cochins and Jersey Giants are going to need a lot more room than Silkies and d'Uccles. The absolute minimum for medium sized birds (sex-links, australorp, faverolle, etc) is about 3 sq ft. in the coop and 10 in the run. What about winter? chickens tend to spend more time in the coop than in the summer.
Generally birds need about 5 square feet per bird in the coop and 10 square feet per bird in the run. The more room the better. I give my birds even more room than this. The lowest in the order NEVER has enough room. LOL