Both in the UK and
the US (and Australia - and let's face it they know a thing or two about
wool) - we have all developed a method of describing wool weights, which
is related to how they are spun rather than having any true meaning in
terms of what tension they will knit to. For example, in the UK, a 2-ply
wool is very fine lace-weight wool, and yet "2 ply" just means
how many strands of spun thread have been used to make the final yarn
- the "single" many be very thick indeed and a hand spun 2 ply
is often a double knitting or an Aran weight. In the US, a worsted yarn
is a medium weight, all-purpose "double knitting"; however,
worsted yarn actually means spun with the fibres all aligned down the
length of the yarn, making a very smooth strong yarn; again, nothing to
do with the thickness. Australians tend to focus on using "ply"
- as the ply goes up the yarn is thicker.
When trying to translate
from one wool quality to another, it is important to check the yardage.
The yardage can vary a lot, pure wools being denser than man-made fibres,
for example. So work out how many yards were required as stated in the
pattern, and then divide by the yards per skein or ball in the wool you