Knitting needle size converter
Convert knitting needle sizes between US, metric (mm), old UK/Canadian and Japanese sizing.
That's about the same as the needle for worsted yarn.
What it means
Which yarn suits that needle?
Typical needle sizes for each yarn weight; the ball band and your tension swatch have the final word.
Every unit
That needle in every system
Learn
Three things worth knowing
-
US 6 = UK 8 = 4 mm
The pivot to remember. US 8 is 5 mm and US 10 is 6 mm; each US step near the middle adds half a millimeter.
-
Why UK sizes run backwards
Old British needle sizes came from the Standard Wire Gauge, where a higher number meant a thinner wire, so a UK 14 is the thinnest common needle.
-
Same number, different needle
A US 8 (5 mm) and a UK 8 (4 mm) differ by a whole millimeter: enough to change a sweater by a full size.
Shortcuts
Popular needle size conversions
Background
About knitting needle sizes
The metric size is the needle’s diameter in millimeters, and it is the one to trust. US sizes count up with the diameter (US 8 is 5 mm), old UK and Canadian sizes count down (UK 8 is 4 mm), and Japanese sizes step 0.3 mm at a time.
Some sizes have no exact match in another system, so a pattern written for US 10¾ wants a 7 mm needle that UK sizing calls 2.