Knitting Needle Size Chart: US, Metric and Old UK Conversions

A US 8 knitting needle is 5 mm. It is a common size for medium weight (worsted) yarn and for many beginner projects like scarves and hats. Old UK and Canadian size 6 is roughly the same diameter.

Metric sizes measure the actual diameter in millimeters, while US numbers are a traditional scale. Because the US scale has fewer steps, sizes like 3.0, 3.125 and 3.25 mm can all be sold as US 3. Pattern gauge matters more than the number, so check the millimeter size when switching brands.

Yes. On the old UK and Canadian scale, higher numbers are thinner needles, the opposite of the US scale. A UK 14 is about 2 mm, while a UK 000 is about 10 mm. Most modern UK patterns now use millimeters, but vintage patterns still use the old numbers.

Use a needle gauge: a flat card with holes sized in millimeters. Push the needle through the smallest hole it fits without forcing. Measure the shaft, not the tip, and remember that circular needle cables do not affect size.

Most beginners do well with US 8 to 10 (5 to 6 mm) needles and medium weight yarn. The stitches are big enough to see and count, and the needles are comfortable to hold. Very small needles make fiddly stitches, and very large needles can feel awkward at first.