There are claimed "minimums" but I wouldn't go that low myself. Lay out some 17" squares all connected in a grid the size of the coop floor and decide if you were the size of a OEGB would you want to be that close to all the other chickens filling those squares?
BTW, 2 sq ft in the coop is the "minimum" for large fowl. Even more ridiculous unless the birds are in the coop ONLY when they are sleeping (in which case they would be on the roosts) or waiting to be let out into the MUCH bigger run. Can barely open their wings in a 17" square.
I used the coop/run size large fowl guidelines for my bantam cochins. 48 sq ft (12' x 4') open air coop/run for four birds at first, lost one so three lived there for 10-11 years. I even had an additional two 12' x 2' chunnels under my plant benches for them. Honestly, to me it would have seemed small for standard hens (the guidelines DO say "minimum"), but seemed "about right" for bantams. Now I can't say for certain that the lack of harsh pecking order behavior I saw was due to the gentleness of the breed or the amount of space they had, but it was probably both factors.
I need to get some new chicks now that the old ladies have passed. Been missing them.