If Aussie sizing is anything like UK sizing, which I am guessing it is based on my experience, I think an Aussie 12 would be a US 8. But nothing is ever certain with sizing. Take into account how fitted the garment is, how stretchy it is, and what the reviews (if any) say. You may end up being a 6 or 10 if the garment runs large or small. If something is fitted where you are largest (like if you have pearish hips), you might also need to size up.
I don't advise going by the size chart though. I think according to Nordstrom's size chart, I am supposed to be an 8, and I have never even come close to being an 8 in my entire life. No idea where those numbers come from!
I know even after conversion, US sizes generally run large compared to Euro sizes, but I do not know how they compare to Aussie sizes. In other words, as a US size 2 I am supposed to be a Euro size 32, but in reality I am more like a 34 or 36. I don't think I could get a 32 past my knees. But conventional sizing conversions don't quite work because Euro clothes are cut slimmer. I guess Tam can tell you if Aussie and US clothes are cut similarly or not.
I'm not certain of how helpful that was..
