How many chickens can my coop/run hold?

[justplainbatty]

that is the outside dimensions so yes I think that's the floor space as well with roosts and the nesting box is attached so that adds a little more the food and water are not kept inside the coop

Ok, good not to take up floor space with food and water, but roosts and nest boxes don't count as space.The reason is that roosts are almost exclusively for sleep and nest box is only to lay an egg or brood. Chickens are off roost during the day and do not stay or sleep in nest boxes unless brooding or sick. The very minimum roosting/sleep space per bird is 8 inches. Your run is a nice size for sure but should your birds need to be confined for some reason, adequate floor space and roost space is a must for their health and well being.