Although I’m not a huge fan of her bare basics books, Delia Smith’s website is a very useful reference point. She has a helpful table of conversions here that are especially good when you’re trying to convert a recipe using American cup measurements to metric but, alas, there are no references to the New Zealand or Australian cup. I didn’t initially realise that these measurements were different – a cup is a cup is a cup, right? – but apparently not.
Apparently the US standard cup is smaller than the NZ/Australian one, about 240ml as opposed to 250ml (depending on who you’re reading). Also, just to really confuse matters, the tablespoon in Australia is 20ml instead of the international standard of 15ml! Unless you are baking with a very precise recipe (and mine tend not to be), these differences shouldn’t cause too many problems – after all, I’ve gotten away with using Kiwi cups for American recipes before this – but it’s just something to be aware of. I think the best way around it is to have two sets of cups. Then you’ve no excuse for bellyflopping cakes and the like!