how big of a coop do i need for 23 chickens?

Honestly, you're going to need a lot more coop space.  The general rule of thumb is 4 square feet per bird in the coop and 10 square feet per bird in the pen (not pin).  Your 5x8 coop is 40 square feet which is big enough for 10 adults.  Your pen, at 300 square feet is good for 20 birds, so you can probably get away with putting 23 in it, but you will need to expand your coop quite a bit.  For roost space, allow about 15" per bird, but you will also need space for nest boxes (5-6 for that number) and a dry place for feed.  Plus, on days when the weather is not conducive to them going outside, they need enough space to move around that they don't end up feather picking each other due to over-crowding.

Agree.  23 chickens might roost up in what you have, perhaps, but that's about all.  23 full sized birds require a LOT of space during those cooped up days of storms and nasty weather.  

I also think the "run" for 23 chickens simply couldn't be large enough.  About a half acre would be just about right.     But seriously, the run should be huge.  In a few days, is is little more than a dirt/mud/dust outdoor cage.   Think BIG.  You'll never regret it.

Quote:

Originally Posted by Fred's Hens 
About a half acre would be just about right.    

x2.  Actually I did mean to add that more is definitely better but forgot - I'm glad Fred was on the ball.  As he said, with too little area, they will eat all the grass, roots and all, and it will be a barren, muddy area thereafter.  If you were able to provide 2 runs the size you have now and alternate them to rest in between, that would be another option.

I'm building a new three sided coop right now . The coop is 140 sq ft & the run is 280 sq ft its pretty big. I'm gonna put 25 pullets in it. I like alot of room for my birds. I have another three sided coop can't remember the coop size but the total measurements together is 330 sq ft & I have 16 hens & one roo in it. My four sided coop which I'll never build another one is 80 sq ft coop & 150 sq ft run houses 10 hens so you can see I give them plenty of space. They all still gripe everyday wanting to get out. You can't ever please them. Biggers always better in my mind.

I'm building a new three sided coop right now . The coop is 140 sq ft & the run is 280 sq ft its pretty big. I'm gonna put 25 pullets in it. I like alot of room for my birds. I have another three sided coop can't remember the coop size but the total measurements together is 330 sq ft & I have 16 hens & one roo in it. My four sided coop which I'll never build another one is 80 sq ft coop & 150 sq ft run houses 10 hens so you can see I give them plenty of space. They all still gripe everyday wanting to get out. You can't ever please them. Biggers always better in my mind.

RH, It"s time to break out the CAMERA !

We're gonna  build a hen house that measures 8ft by 10ft. i'm thinkin that would hold about 20 hens comfortably. Does that sound about right? \i'm not sure how big the run should be.

Poor birds. No room.