Coop size and # of nesting boxes for 18 future hens

First time chicken owner. No one ever mentions how fast these girls grow. I am on day 19 and have been reading old threads on coop building etc. Currently all 18/18 hens are all alive and happy. My question is will a 6'Lx10w'x6'h elevated so prob actual 4' high coop with 4 built in nesting boxes be enough for these girls. The run will be attached later.

Not going with a pre-built due to numerous negative reviews I've read.

Any advice tips etc. Thank you