We have some from Tractor Supply on the windows to keep things from coming in that way but I don't know what gauge it is. It's just what they had. Sorry.
I can warn you about nasty messes on wire floors though. I had the hens in those rabbit hutches you get from Tractor Supply that you buy a black pan to go under and the poop didn't fall through very well. Its hard to clean unless you take it outside and scrub it with a brush. Wear googles when you this! Trust me. You've heard of the poop hitting the fan? Its nothing compared to the wet chicken poop hitting the bristles of the brush. Maybe someone here knows a better way to clean wire. I hope so!
I just bought what Home Depot had too. It was 1/2 inch holes. I think the higher the gauge, the thinner the wire. I think Home Depot's 1/4 inch hole hardware cloth is a thinner gauge. I used the 1/2 inch hole hardware cloth over my entire run and over every window and ventilation area of my coop (not the floor though. I have a solid floor with 6 inches of wood shavings on it). I know I have lots of major huge raccoons living in the trees in my yard and so far so good. Not even a small sign of breaking in.
I can warn you about nasty messes on wire floors though
Just a comment: chickens shouldn't ever be on total wire flooring. It can damage their feet/legs. I use a rabbit hutch for my broodies and laid down flat boards over all the wire with shavings on top of that. It makes it really easy to clean, just scoop out the poop and put some clean shavings down.
I use a lot of hardware cloth building a coop and run. I have solid floors, but have hardware cloth under the floor and several feet up the walls to keep the vermin from gnawing their way in. I also use it as the lowest level of wire on my run. It's buried 18 to 20 inches deep all the way around and up the first three feet.
I've had raccoons, dogs, and a bobcat all try to get in without any success.