US to Metric Knitting Needle Conversion
Find the exact millimeter (mm) equivalent for every US knitting needle size — plus UK sizes and yarn weight pairings in one complete chart.
US 6 = 4.0 mm · US 7 = 4.5 mm · US 8 = 5.0 mm · US 9 = 5.5 mm · US 10 = 6.0 mm
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US to Metric (mm) Conversion Chart
Every standard US knitting needle size with its metric equivalent, UK size, and recommended yarn weight. Approximate Japanese equivalents are shown where no exact match exists.
| US Size | Metric (mm) | UK Size | Japanese | Yarn Weight |
|---|---|---|---|---|
| US 000000 | 1.5 mm | — | — | Lace / Cobweb |
| US 00000 | 1.75 mm | — | — | Lace / Cobweb |
| US 0 | 2 mm | 14 | 0 | Fingering / Sock |
| US 1 | 2.25 mm | 13 | ~1 (approx) | Fingering / Sock |
| US 1.5 | 2.5 mm | — | — | Fingering / Sock |
| US 2 | 2.75 mm | 12 | ~3 (approx) | Sport / DK |
| US 2.5 | 3 mm | 11 | 4 | Sport / DK |
| US 3 | 3.25 mm | 10 | ~5 (approx) | Sport / DK |
| US 4 | 3.5 mm | — | ~5 (approx) | DK / Worsted |
| US 5 | 3.75 mm | 9 | ~6 (approx) | DK / Worsted |
| US 6 | 4 mm | 8 | ~7 (approx) | DK / Worsted |
| US 7 | 4.5 mm | 7 | ~8 (approx) | Worsted / Aran |
| US 8 | 5 mm | 6 | ~9 (approx) | Worsted / Aran |
| US 9 | 5.5 mm | 5 | ~11 (approx) | Bulky / Chunky |
| US 10 | 6 mm | 4 | ~12 (approx) | Bulky / Chunky |
| US 10.5 | 6.5 mm | 3 | — | Bulky / Chunky |
| US 11 | 8 mm | 0 | — | Super Bulky / Jumbo |
| US 13 | 9 mm | 00 | — | Super Bulky / Jumbo |
| US 15 | 10 mm | 000 | — | Super Bulky / Jumbo |
| US 17 | 12 mm | — | — | Super Bulky / Jumbo |
| US 19 | 15 mm | — | — | Super Bulky / Jumbo |
| US 35 | 19 mm | — | — | Super Bulky / Jumbo |
| US 36 | 20 mm | — | — | Super Bulky / Jumbo |
| US 50 | 25 mm | — | — | Super Bulky / Jumbo |
Understanding US Needle Sizes
US knitting needle sizes run from 0000 (approximately 1.25 mm) up to size 50 (25 mm). Unlike metric sizing, the US numbers are not direct measurements of the needle's diameter — they are an arbitrary scale that developed historically within the American craft industry.
This is why you'll see apparent inconsistencies: a US size 7 is 4.5 mm, while a US size 6 is 4.0 mm, and the gap between sizes is not always equal. The metric measurement stamped on your needle is always the most reliable reference.
US sizes in the most popular range
Most knitting patterns call for needles in the US 5–10 range (3.75–6.0 mm). This covers DK, worsted, and aran weight yarns — the yarns most commonly used for garments, hats, scarves, and blankets. If you're buying your first set of needles, a range of US 6–9 covers the majority of published patterns.
When a pattern lists metric but you only have US sizes
Find the mm size in the table above and read across to the US column. If the exact mm isn't listed (for example, a pattern asks for 3.9 mm), go to the nearest standard size. Always knit a gauge swatch to confirm your stitch count matches the pattern before starting a project.
US vs. Metric: Key Differences
The metric system measures the actual physical diameter of the needle shaft in millimeters. It's the universal standard used across Europe, Australia, and most of Asia. US sizing is primarily used in American patterns and on needles sold in the United States.
Modern needles from most major brands (Addi, ChiaoGoo, Knit Picks, HiyaHiya) are labeled with both the US size and the mm measurement. If your needles only show one system, use the chart above to find the equivalent.