I know this question has probably been asked a million times. I have 16 5 week old pullets (I think) so I'm was thinking 8 nesting boxes. So how deep, wide should they be. Should the top be open or does that really matter. I have seen both ways.
It would help if you had said what breed. 12x12x12 is commonly used, but I feel a little small for heavy breeds. One for every 4 hens is plenty; often they all line up to use the favorite nest anyhow. You can build them most any way you want, or use 5 gallon buckets, milk crates, cardboard boxes, etc. Good idea for there to be some holes for air movement. Also a good idea to have about a 3" or 4" lip across the bottom to hold the bedding and eggs in. If you put a top on them, make it at a 45 degree angle to prevent their pooping on it. Or make it flat, put a dropping board on top, and build the roost above the nests.
The normal ratio is 4 hens per nesting box, so you would need 4 total individual nesting boxes, not 8.
You'll get a lot of discussion on size. For full sized fowl, I'd consider 12" x 12" the minimum. I personally used 16" x 16" as the hens often like to lay together and I think this gives them more room so maybe less eggs get broken. I really don't know if this actually keeps eggs from getting broken or not.
I'll include a link to community nesting boxes that might interest you. People obviously do many different things and almost all of them work.
Not sure if this helps but my vote is for having a top on the nesting boxes. Guess the other measurements would depend on the size of the grown birds.
By observation, my hens have always perferred a nest that is more closed in, ie: roof, 3 sides preferably with a raised lip on the front opening - anything that really gives them a sense of privacy.
Throughout the years, my hens have nested ALL OVER the place. My husband especially loves it when they start flying out of the hen yard and nesting around his shop area! Guaranteed to illicit colorful speech & plenty of threats - LOL! They always choose places (or nesting boxes) that allow them to 'hide out'. Even if that means a very deep horse bucket filled with a little left over hay
We have utilized several items around our place throughout the years, even an old 6 cage rabbit hutch which has divided sections in it. While some will nest in these more open areas, most of my hens prefer the smaller, more cozy nests.
I know I thought about that after I posted.
1 turken, 1 barred rock, 2 lackenvelder's, 2 golden comets, 2 brown leghorns, 2 white leghorns, 3 white plymouth rocks, and three black australorps