Knitting needle sizes in US numbers, millimeters and old UK sizes, with the yarn weights for each.
How it works
Knitting needles are sized by diameter: millimeters everywhere, US numbers in the United States (US 8 is 5 mm), and old UK / Canadian numbers on older needles and patterns (UK 6 is 5 mm).
Old UK numbers run the other way: the bigger the number, the thinner the needle.
Pick a needle to see the yarn weights it suits and the crochet hook of the same size.
Frequently asked questions
What is a US size 8 needle in mm?
5 mm (old UK size 6). It suits worsted (medium) yarn.
What needles do I use for worsted yarn?
The Craft Yarn Council suggests 4.5–5.5 mm, US 7 to 9.
Why don’t UK and US needle numbers match?
Old UK numbers come from a wire gauge where bigger numbers are thinner; US numbers grow with the needle. Millimeters are the same everywhere.