Free knitting tool
Old knitting needle size converter
Vintage British patterns give needle sizes like “No. 10” or “No. 13”, and they run the opposite way to metric: the bigger the number, the finer the needle. Choose the sizing system your pattern uses and the size it asks for, and we’ll show you the metric, US and Japanese equivalents. Where no modern needle matches exactly, we say so and give you the nearest sizes either side.
Convert a needle size
Full needle size chart
Every row is one physical needle thickness. A dash means that system has no size at that thickness.
| Metric | Old UK / Canadian | US | Japanese |
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How this works, and its limits
- We use the conversions found on established needle charts, which agree on almost every size. Old UK and Canadian sizes are the same system.
- Old UK numbers came from the imperial wire gauge, so an original needle can be a fraction of a millimetre off its modern metric partner (an old No. 9 is about 3.66 mm, sold today as 3.75 mm). That’s why your tension square matters more than the number.
- Some sizes have no exact partner: metric 2.5 mm, 3 mm, 3.5 mm, 7 mm and 7.5 mm have no official US or UK match in at least one system, and old UK No. 16 has no metric size at all. Japanese sizes (2.1 mm, 2.4 mm and so on) mostly fall between metric sizes.
- Some brands label 2.5 mm as US 1½, 3 mm as US 2½ and 7 mm as US 10¾. These aren’t official US sizes. A few charts also list old UK 13 as 2.5 mm rather than 2.25 mm.
- Old American steel double-pointed needles used their own numbering, so this chart may not match them.
- Japanese sizes stop at No. 15 (6.6 mm). Thicker Japanese needles are sold by millimetre.
Whatever the size, knit a tension square (gauge swatch) and change needles until your stitches match the pattern.
Want a vintage pattern already rewritten for your size and gauge? Browse our patterns. For the history behind these numbers, read our guide to old knitting needle sizes.