Hope nobody minds that this is a sort of supplementary topic to the one posted by Brandy-M about sock needles.
Jan says she uses a US size 1 needle and Mrs Levite a US size 2.
According to this chart: http://www.fibergypsy.com/common/needles.shtml
A US size 1 can be either 2.25 mm or 2.5mm
A US size 2 can be 2.75 mm or 3mm
Could some kind soul please tell me that if a US pattern stipulates Size 1 or Size 2, how do you know which needle size to use?
Do you have to buy both, or what?
It would be really useful to know (especially to Brits, Aussies and Kiwis) which is the more 'usual' size referred to in knitting patterns.
Does anyone know why there is this ambiguity about these two sizes?