The usual rule of thumb you read is 4 square feet per bird indoors, plus 10 square feet per bird outdoors. However, the more space birds have to move around in, the better for them and for you. Your clean up duties are reduced, and the birds behave in a more natural and interesting way.
The larger the flock, the more possibilities for social problems, too. I've wondered what the natural flock size for wild jungle fowl is. I have a sister who at one time had 14 dogs (they knew she was a soft touch at the local animal shelter). Once her pack got over 8 or 9 dogs, she started seeing problems. It got so bad one of the smaller dogs was killed by the pack. She had to find homes for several of the dogs, and once she got the pack down in size, the social problems stopped.
I have a couple of hundred chickens and some are in coops that are breed specific however if I'm not collecting eggs for hatching they are all allowed to free range together. They will usually stay with their own coop mates and only have the occasional rooster stand off because someone looked at someone elses hen. Last night a bad storm came in and before I could get home and off the tractor there were about 20 chickens in a 4'X4' coop with a 12'X12' run attached, they were packed in there tight with 3 roosters in the same coop. That coop usually holds 4 hens and a rooster. What size birds do you have bantams or large this changes things you can fit more bantams into a smaller space. Consider free ranging them then all you need is space for roosting and nesting you could get lots of birds in the area you described.
I have bantams, At this point I will not be able to free range to due to dogs, They are housed in my back yard, which is two lots. have plans to fence the dogs off on one lot and allow these guys to roam the other lot?
Well...some would say if you have bantams, your coop housing could accomodate 20 bantam birds. The "rule of thumb" for bantams is a minimum of 2 sq. ft. each of housing. However, if your weather is such that they might be confined at times, due to heat or cold, either by their choice or yours, then I personally wouldn't try that many... Your run will accomodate more birds than your housing.
My birds refuse to go out if there is snow on the ground. So I have to have a bigger coop to make up for them not going out in bad weather. OR I build a run that keeps the snow out.
Right now I have a 20x30 run= 600sq ft I could have 60 birds. Hmmmmm Don't think so. My coops are Plastic Playhouses. One holds 4 full grown birds, one holds 4 OEG's and the 3rd will hold a dozen(it's bigger and set up better than the other 2)
My run has a metal roof at the corners to help to give them shade and a way to get out of the weather.