Knitting Needle Size Converter
Enter your needle size in any one system and instantly see its equivalents in US, metric millimeters, and UK.
📖 How it works & FAQWhy needle sizes need converting
Knitting patterns come from all over the world, and each region labels needles differently. US sizing uses its own numbered scale, the UK (and older Australian) system runs the numbers in the opposite direction, and most of the world simply measures the needle's diameter in millimeters. A pattern that calls for a "US 8" means nothing to a shop selling "5 mm" needles unless you can translate. This converter uses the standard equivalence table so you can shop, swap, and follow patterns from any source with confidence.
Millimeters are the real measurement
The millimeter value is the actual diameter of the needle shaft, so it is the most reliable number. US and UK labels are just conventional names mapped onto those diameters, and a few metric sizes (like 2.5 mm or 7 mm) have no exact US or UK equivalent at all. When two systems disagree or a size is missing, always trust the millimeters and match your gauge swatch rather than the label on the packaging.
How to use it
- Choose which system your size is in — US, metric millimeters, or UK.
- Pick your needle size from the second dropdown.
- Read the matching US, metric, and UK values in the result box below.
- Watch for a "no size" note, which means that diameter has no standard equivalent in that system.
Everything runs in your browser — nothing is uploaded or stored.
FAQ
- Is US 7 really 4.5 mm?
- Yes. US 7 equals 4.5 mm equals UK 7. US 8 is 5 mm (UK 6), and US 6 is 4 mm (UK 8).
- Why do UK numbers go down as needles get bigger?
- The old UK/Imperial scale was numbered in reverse, so a smaller number means a thicker needle — the opposite of the US scale.
- What if my size shows "no size"?
- Some millimeter diameters have no official US or UK label. Use the nearest millimeter size and check your gauge swatch to be sure.
- Are these conversions exact?
- The millimeter diameters are exact; the US and UK labels are standard equivalents. Brands vary slightly, so knit a gauge swatch when fit matters. Treat cross-system labels as a close guide.