The complete reference for US, UK/Canadian, and Metric (mm) needle sizes — all regions, one page.
Get exact mm equivalents to avoid pattern sizing errors.
| Metric (mm) | US Size | UK/Canadian |
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Have you ever bought a vintage British knitting pattern that calls for a "Size 8" needle, only to realize the US Size 8 and UK Size 8 are completely different? Needle sizing conventions are notoriously inconsistent worldwide. This converter instantly translates between US, UK/Canadian, and universal Metric (mm) sizes to ensure you use the correct needle diameter, preventing massive sizing errors in your garments.
The Listed Size: Check your yarn label or pattern instructions to find the recommended needle size.
The Region Context: Determine if your pattern is American (using US numbers like 6, 7, 8) or British/Vintage (using descending UK numbers like 10, 9, 8).
Use the global toggle in our site's navigation bar to choose whether you want to start from a US Size or a Metric (mm) Size.
Click the dropdown menu and select the needle number printed on your pattern.
The tool instantly reveals the exact Metric (mm) diameter and the cross-regional equivalents.
The most important piece of information returned is the Metric (mm) diameter. Because manufacturers can vary slightly in how they interpret US numbers, the exact millimetre size is the only objective measurement of a needle's thickness. Use the mm measurement to confidently select the correct needle from your physical stash.
Scenario: You are following a pattern that asks for a US Size 6 needle, but you live in Europe and only have mm needles.
Input: Select US 6 from the dropdown.
Conversion Math: The tool cross-references the standard sizing database.
Result: 4.0 mm. You should pull a 4.0 mm needle from your stash. It also shows this is equivalent to a vintage UK Size 8.
US needle sizes increase as the needles get thicker (e.g., US 1 is very thin, US 15 is very thick). The traditional UK system uses Standard Wire Gauge measurements, which decrease as needles get thicker (e.g., UK 14 is thin, UK 000 is thick). This is why relying on Metric (mm) is universally preferred today.
Some needle manufacturers vary slightly. A US 7 is technically 4.5 mm, but some brands produce US 7 needles that measure 4.5 mm, while others might measure closer to 4.25 mm. When in doubt, buy a cheap needle gauge tool and measure the physical needle.
Yes. A slick metal needle allows stitches to slide freely, which can loosen your tension. A grippy wooden or bamboo needle creates friction, often resulting in tighter stitches. If you switch materials halfway through a project, your gauge will likely change even if you use the exact same mm size.