Knitting needle sizes: conversion chart (US, UK & mm)
Convert knitting needle sizes between US, UK (old Imperial) and metric mm in one clear chart. Plus which needle size to use for each yarn weight.
By Julia WallinKnyt Co-founder and editorKnitting needle sizes are measured three ways: metric (millimetres), US numbers, and old UK/Imperial numbers. The metric size is the only fully reliable one, because US and UK numbering varies between brands. The chart below converts all three, so you can translate any pattern or needle no matter where it was written. When in doubt, go by the millimetre measurement.
Needle size conversion chart
| Metric (mm) | US size | UK / Canada (old Imperial) |
|---|---|---|
| 2.0 mm | 0 | 14 |
| 2.25 mm | 1 | 13 |
| 2.5 mm | 1½ | none |
| 2.75 mm | 2 | 12 |
| 3.0 mm | none | 11 |
| 3.25 mm | 3 | 10 |
| 3.5 mm | 4 | none |
| 3.75 mm | 5 | 9 |
| 4.0 mm | 6 | 8 |
| 4.5 mm | 7 | 7 |
| 5.0 mm | 8 | 6 |
| 5.5 mm | 9 | 5 |
| 6.0 mm | 10 | 4 |
| 6.5 mm | 10½ | 3 |
| 7.0 mm | none | 2 |
| 7.5 mm | none | 1 |
| 8.0 mm | 11 | 0 |
| 9.0 mm | 13 | 00 |
| 10.0 mm | 15 | 000 |
| 12.75 mm | 17 | none |
| 15.0 mm | 19 | none |
| 19.0 mm | 35 | none |
| 25.0 mm | 50 | none |
US to metric values per the Craft Yarn Council Hooks & Needles standard, cross-checked against Vogue Knitting. UK Imperial sizes follow the traditional British numbering. "None" marks sizes with no standard equivalent in that system. Some brands also offer US half sizes, for example US 1½ = 2.5 mm, US 2½ = 3.0 mm, US 10½ = 6.5 mm.
Why metric is the size that matters
US and UK needle numbers were never fully standardised, and they run in opposite directions. In the US, a bigger number means a bigger needle. In the old UK system, a bigger number means a smaller needle. The millimetre measurement is a direct physical measurement of the needle's diameter, so it does not depend on brand or country. Whenever a pattern and your needles disagree, trust the mm.
A note on "old and new" UK sizes: the UK switched from Imperial numbers (14, 13, 12 and so on) to metric (2 mm, 2.25 mm and so on) decades ago. Older British patterns and inherited needles use the Imperial numbers in the right-hand column above. Modern UK patterns use millimetres, the same as everywhere else.
Which needle size should I use?
Your pattern will tell you. If you are choosing yourself, match the needle to your yarn weight. As a rough guide:
| Yarn weight | Typical needle (metric) | US |
|---|---|---|
| Lace (0) | 1.5 to 2.25 mm | 000 to 1 |
| Super fine / sock (1) | 2.25 to 3.25 mm | 1 to 3 |
| Fine / sport (2) | 3.25 to 3.75 mm | 3 to 5 |
| Light / DK (3) | 3.75 to 4.5 mm | 5 to 7 |
| Medium / worsted (4) | 4.5 to 5.5 mm | 7 to 9 |
| Bulky / chunky (5) | 5.5 to 8 mm | 9 to 11 |
| Super bulky (6) | 8 to 12.75 mm | 11 to 17 |
| Jumbo (7) | 12.75 mm and larger | 17 and larger |
Guidelines from the Craft Yarn Council; see the full yarn weights chart →. These are starting points. The needle size that gives you the pattern's gauge always takes priority over the size on the label.
What about Japanese needle sizes?
Japanese patterns use their own numbering (the "号" or gō system) and metric. If you are working from a Japanese pattern, convert via the millimetre size, which is the common reference across all systems.
Frequently asked questions
What is a US 8 knitting needle in mm?
A US 8 is 5.0 mm. In the old UK system that is a size 6.
What is a 4 mm knitting needle in US size?
4.0 mm is a US 6 (and an old UK size 8).
Why are US and UK needle sizes numbered differently?
They developed separately and were never standardised together. They also run in opposite directions: US numbers increase with size, old UK numbers decrease. The metric (mm) measurement avoids the confusion.
What does "old and new" UK needle sizes mean?
"Old" refers to the traditional British Imperial numbers (14, 13, 12 and so on). "New" refers to the metric millimetre sizes the UK adopted later. Old patterns use Imperial. Modern ones use mm.
Which needle size is best for a beginner?
A mid-range 4.5 to 5.5 mm (US 7 to 9) with a smooth worsted-weight yarn is the easiest to handle while learning. It is big enough to see your stitches and not so big that it is awkward.
Co-founder and editor of Knyt. Avid knitter!
