What square footage is the pen and how many chickens will be there?

I might try this sometime... and am curious what you think the area requirements are per hen?

People used to raise chickens primarily on forage, but I've found very little data about space requirements (with numbers on the internet ranging from 10 to 100 chickens per acre.) So we're very much in the experimental stages right now, trying to figure out the best way to go. Here's our plan:

• Build three small pastures that we can rotate the chickens through, preventing bare earth from forming when chickens overscratch in any one area. (I don't know how big "small" will be. I'll have a better idea once we put our 25 birds out on the first pasture and see how long it takes for them to eat it up.)
• That said, let the chickens scratch the first, flat area down to bare earth so that we can plant grains to turn the chickens into in the fall.
• It won't be in production this year, but I've planted an everbearing mulberry which is reported to provide all of the food a flock of chickens will need for two months in the summer. I've also put in some Nanking cherries. I hope that adding good food plants like this will let me keep more chickens on forage in a smaller space.
• We're also hoping to get free food waste from the grocery store and build a bit black soldierfly bin to supplement their feed.

Which is all to say --- I have no clue what we're doing, but we're sure having fun! If you know anyone who has successfully raised chickens on forage alone, I'd appreciate it if you sent them to our chicken foraging poll. I keep begging people to give me information about raising chickens on forage, and no one does!