Knitting Needle Size Conversion Chart
Convert between the US needle numbering system, the old UK system and metric millimetres. Metric is the international standard; US and UK numbering run in opposite directions.
| Metric (mm) | US | UK (old) |
|---|
Standard: ISO 2560 (metric sizes) · Data checked: 2026-10-14
Frequently asked questions
Why is my US 8 different from a UK 8?
Because the two scales run in opposite directions and were never aligned. US sizes increase with diameter; the old UK and Canadian sizes decrease. A US 8 is about 5 mm; an old UK 8 is 4 mm. Since the scales crossed, some numbers refer to very different needles.
What is the mm size for a US 8?
About 5.0 mm. US 8 is roughly 5 mm, US 6 is 4 mm, US 10 is 6 mm. Always work from the millimetre figure if a pattern gives one — it is the only unambiguous number.
Do I need the size the pattern says?
You need the gauge the pattern says. Needle size is the means, not the requirement. Knit a swatch with the suggested size and change needles until the gauge matches, because everyone's tension differs.
What is the difference between straight, circular and DPN needles?
How you hold the work. Straight needles are for flat pieces; circular needles take a large number of stitches and can be used flat or in the round; double-pointed needles are for small circumferences like socks and cuffs. The size number means the same thing on all of them.