Over the years, I collected a whole LOT of all kinds, and sizes of (scrap, or "drop") electrical wire, and I found that a lot of it was unmarked as to gauge. I found this chart, and if you have a micrometer, or vernier caliper, you can determine wire size (gauge) by it's diameter.-
4 gauge = .204
6 gauge = .162
8 gauge = .128
10 gauge = .101
12 gauge = .080
14 gauge = .064
16 gauge = .050
18 gauge = .040
I hope this helps a few of you guys. It is sure helping me right now.....