I don't have any chicks or chickens. But I did sleep in a Holiday Inn Express last night!

<sigh> I had to rehome my entire flock in August due to health and travel issues. But I had them for so long I still get my past and present tenses mixed up when I'm enthusiastically typing away!

I've learned so much here, and with good old common sense and hands-on experience, so just because I don't have chickens anymore doesn't mean what I've learned and done goes away.
As for the size of your coop and number of chickens it can hold, that's one question I have always avoided like the plague! I'm a coward, and extremely mathematically challenged - as in I have to count the dots on the dice when we play Yahtzee and I can't even
hire a cribbage partner! So all that "so-many-square-feet-per-bird = this-size-setup and this-many-birds-housed" totally escapes me. I'd be lying if I said otherwise and gave really bad answers.

Best I can do is direct you to the page for our setup and tell you how many birds, ranging in size from Silkies to Light Brahmas, we had in ours. You can click on "My Coop" under my avatar to see it. At times we were way too overcrowded and had to make adjustments to the number we had, processing those who were poor layers, had nasty temperaments, or when we ended up with an excess of roosters. Our flock was usually around 12 birds on average, but did get up to 22 before our number went back down. Our coop was 6'x8'. Think I'm joking about being mathematically challenged? I couldn't even get the numbers transferred correctly from the draft sketch to the final sketch - that's how I ended up with a coop that was also 8 feet tall at the front and 6 feet tall at the back. Woe is me! Ventilation wise it turned out to be a brilliant move, but the guys did NOT have fun putting up the rafters and putting on the roof!
Our run was a hoop run...that was easy enough. Just cattle panels, and it was a very nice size! (You're not gonna ask me precisely how big after learning all this, are you?) We didn't really measure...we just took a panel, arched and walked it between the two of us, and when it looked like the interior was a good size and I could stand up and work comfortably in it, we dropped rocks on the ground where the fence posts would go to hold it up! Then on to the next panel. Real scientific! When we decided we needed to expand it, we just took off the end panel, pounded two more steel fence posts into the ground, arched a new panel and tied it in to the existing panel, then put the end cap back on. We can reduce the size by doing the same thing in reverse. The beauty of the run, in addition to it's size, was the fact that it held up to snow, rain, heavy winds in the 40 - 60 mph range, (one gust of 90 mph, officially recorded by the NWS), and it didn't budge or need a single repair the entire time we had it up. It still doesn't, and with plastic put up over it it now makes a perfect greenhouse, with the coop being the garden shed. Not a single penny of the construction costs lost.
This run, mostly covered with plastic in winter, is where we set up our x-pen brooder and raised our chicks, even with snow blowing sideways and temps in the twenties!