Clover
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Knitting needle size chart & converter: mm, US, UK, Japanese
Convert knitting needle sizes between metric (mm), US, old UK and Japanese numbers, and see which needles suit each yarn weight.
The same needle in every system appears on the right. Where two systems have no exact match, you get the closest size and how far off it is.
Knitting needle size chart
| Metric | US | Old UK / Canadian | Notes |
|---|
Metric and US sizes follow the Craft Yarn Council standard. A dash means no standard size exists in that system.
Japanese needle sizes
| Japanese size | Metric | Nearest US |
|---|
Which needle for which yarn weight
| No. | Yarn weight | Gauge per 4 in | Needles |
|---|
Reading needle sizes
Metric is the only system that describes the needle directly: it is the diameter of the shaft in millimetres. Almost every needle sold today is stamped with its metric size, even when the US or UK number is bigger on the packet, so when two charts disagree, trust the millimetres.
US sizes run from 000 (1.5 mm) to 50 (25 mm) and are the default in American patterns. A few numbers cover two metric sizes because brands round differently: a US 6 can be 4 or 4.25 mm.
Old UK and Canadian sizes were replaced by metric in the 1970s but are still common in vintage patterns and inherited needle sets. They run backwards, from 17 for the thinnest to 000 for 10 mm.
Japanese sizes appear in Japanese pattern books and on needles from brands such as Clover and Tulip. They step up in 0.3 mm increments, so they rarely line up exactly with metric sizes.
Not sure what size an unmarked needle is? Push it through the holes of a needle gauge and use the smallest hole it fits. Need to match a yarn without a label? Try the WPI yarn weight calculator, then check your fabric with the gauge calculator.
How to use it
- Choose the sizing system printed in your pattern or on your needles: metric, US, old UK or Japanese.
- Pick the size. The converter shows the same needle in every other system, and says when there is no exact match.
- Check which yarn weights the needle usually suits.
- Knit a swatch and go up or down a size until your gauge matches the pattern.
Questions
What is a US size 8 knitting needle in mm?
A US 8 needle is 5 mm. It is the old UK size 6 and is a common choice for worsted and aran weight yarn.
Why do old UK needle sizes go down as the needles get bigger?
Old British and Canadian needle numbers came from the Standard Wire Gauge used for metal wire, where a higher number means thinner wire. So UK 14 is a thin 2 mm needle and UK 000 is a thick 10 mm needle.
Are there US sizes for 3 mm, 7 mm and 2.5 mm needles?
Not officially. Some brands label them US 2½, 10¾ and 1½, but the Craft Yarn Council chart leaves them without a US number. When a pattern gives both, follow the millimetre size.
How do Japanese needle sizes work?
Japanese needles are numbered 0 to 15, starting at 2.1 mm and going up 0.3 mm per size, so No. 7 is 4.2 mm and No. 15 is 6.6 mm. Larger Japanese needles are sold by millimetre. Most Japanese sizes fall between two metric sizes, so swatch before you swap.
What size needles should I use for my yarn?
Start with the needle size on the yarn label. As a rough guide, DK (light, 3) yarn suits 3.75–4.5 mm needles and worsted (medium, 4) yarn suits 4.5–5.5 mm needles. The table below lists every yarn weight.
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