Q: What is wire gauge, and why should I care about it?
When you're looking at fencing or hardware cloth for your flock's enclosure, you may run into the term "wire gauge," and wonder that that is, and which is best!
Wire gauge is essentially just a measurement of how thick the wire is. In terms of fencing here in the US, the LOWER the gauge, the thicker the wire. Thicker wire, of course, is sturdier and will provide more predator protection, because predators will be less likely to be able to tear through it. On the other hand, thicker wire will also be harder to manipulate, and will require a lot more work to affix to your run, coop, or fence posts... plus a lot more effort to cut through it! In addition, the thicker wire will be more expensive because it takes more raw material to manufacture.
Thin wire, such as you might find for chicken wire, bends and stretches easily, and is easy to cut or break. So it's easy to use---inexpensive, too!---but not especially secure. This is why you hear us warn so often about using chicken wire to keep out predators: it often doesn't. It's just too thin, and even small, weak predators can get through it. Chicken wire works to contain your flock, but not to keep predators (or rats!) out.
But there are some other fencing considerations you should know about before making your choice.
For example, you'll need to decide if you want twisted or welded wire. Twisted wire is generally less desirable, because it is less strong, than welded wire. Twisted wire like chicken wire is easier for predators to stretch and push through, while welded wire like hardware cloth has to break or be chewed through to misshape to the same extent.
This chicken wire is going to be destroyed by the raccoon
This chicken is more secure with welded-wire hardware cloth
You'll also need to determine if you want it to be galvanized or not---or if you want vinyl coated wire fencing.
Galvanized: we'll just say it. YES. This is what will protect your fence from galvanic corrosion, a fancy way of saying rust. It will add years to the life of your wire. The way it works is that the zinc is a less noble metal. Zinc? Yeah, zinc is a commoner when compared to steel, so it will get corroded first. It's like a thin, sacrificial layer that protects the steel underneath. If the zinc gets scratched, or wears or corrodes away, eventually the steel will corrode, too. Just definitely get galvanized. It shouldn't add much cost in comparison to how much utility you're getting from it. It's a good deal.
Vinyl-coated: this is an additional protection you can get for your fence or wire, where---obviously, right?---there's a thin layer of vinyl covering the metal. This usually adds some cost, but the protection is great! And in addition, it ads thickness to the underlying wire (galvanization doesn't add any significant thickness), so it adds effective gauge and strength to your fence.