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mm (metric)
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US size
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UK / Canada
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Yarn weight
| mm | US | UK / CA | Yarn weight |
|---|
Knitting Needle Size Converter
Needle sizes vary by country. US sizes use numbers (0-50), metric sizes are diameters in millimeters, and the UK/Canada system uses a descending scale where smaller numbers mean larger needles.
Quick reference
| US Size | Metric (mm) | UK/Canada | Yarn weight |
|---|---|---|---|
| 0 | 2.0 mm | 14 | Lace |
| 1 | 2.25 mm | 13 | Lace / Fingering |
| 3 | 3.25 mm | 10 | DK |
| 6 | 4.0 mm | 8 | Worsted / Aran |
| 9 | 5.5 mm | 5 | Bulky |
| 13 | 9.0 mm | 00 | Super Bulky |
| 17 | 12.75 mm | - | Jumbo |
Key facts
- Metric (mm) is the universal standard: when in doubt, use the mm size
- US and UK sizes for the same number do NOT correspond to the same diameter
- Crochet hooks use the same metric system as knitting needles
- Gauge (tension) relates to the mm size, not the US or UK number
- When a pattern specifies a needle size, always check with your gauge swatch, needle recommendations are a starting point
UK vintage patterns and the old numbering system
The old UK/Canada needle numbering system (still found in vintage patterns from the 1940s-1980s) counts in reverse: higher UK numbers mean thinner needles. This is the opposite of US sizing, which creates confusion when following vintage UK patterns:
| Old UK number | Metric (mm) | Typical yarn weight |
|---|---|---|
| UK 14 | 2.0 mm | Lace / cobweb |
| UK 12 | 2.75 mm | Fingering / 4-ply |
| UK 10 | 3.25 mm | DK (double knit) |
| UK 8 | 4.0 mm | Worsted / Aran |
| UK 4 | 6.0 mm | Chunky / Bulky |
| UK 000 | 10.0 mm | Super bulky |
UK vintage patterns also use yarn weights that differ from US names: "4-ply" (UK) = Fingering (US), "DK" = DK, "Aran" = Worsted/Heavy Worsted, "Chunky" = Bulky. Many UK knitting publishers (Sirdar, Patons, Hayfield) still print patterns using UK yarn weight names.