US to Japanese Knitting Needle Conversion (号)
Most US needle sizes don't have an exact Japanese 号 equivalent — the two scales use different millimeter increments. This chart shows the nearest 号 size for every US needle, with the mm gap explained.
Japanese 号 increments (~0.3 mm) don't align with US sizes. Always use the mm value to find the nearest Japanese needle, and always swatch.
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US to Japanese 号 Conversion Chart
Each US size with its mm measurement and the nearest Japanese 号 equivalent. Where no exact match exists, the nearest size is shown with the mm difference noted.
| US Size | Metric (mm) | Nearest Japanese (号) | Japanese mm | Yarn Weight |
|---|---|---|---|---|
| US 000000 | 1.5 mm | 0号 (approx) | 2 mm (±0.5) | Lace / Cobweb |
| US 00000 | 1.75 mm | 0号 (approx) | 2 mm (±0.3) | Lace / Cobweb |
| US 0 | 2 mm | 0号 | 2 mm | Fingering / Sock |
| US 1 | 2.25 mm | 1号 (approx) | 2.1 mm (±0.1) | Fingering / Sock |
| US 1.5 | 2.5 mm | 2号 (approx) | 2.4 mm (±0.1) | Fingering / Sock |
| US 2 | 2.75 mm | 3号 | 2.7 mm | Sport / DK |
| US 2.5 | 3 mm | 4号 | 3 mm | Sport / DK |
| US 3 | 3.25 mm | 5号 | 3.3 mm | Sport / DK |
| US 4 | 3.5 mm | 6号 (approx) | 3.6 mm (±0.1) | DK / Worsted |
| US 5 | 3.75 mm | 6号 (approx) | 3.6 mm (±0.1) | DK / Worsted |
| US 6 | 4 mm | 7号 (approx) | 3.9 mm (±0.1) | DK / Worsted |
| US 7 | 4.5 mm | 9号 | 4.5 mm | Worsted / Aran |
| US 8 | 5 mm | 10号 (approx) | 5.1 mm (±0.1) | Worsted / Aran |
| US 9 | 5.5 mm | 11号 (approx) | 5.4 mm (±0.1) | Bulky / Chunky |
| US 10 | 6 mm | 13号 | 6 mm | Bulky / Chunky |
| US 10.5 | 6.5 mm | 15号 (approx) | 6.6 mm (±0.1) | Bulky / Chunky |
| US 11 | 8 mm | 15号 (approx) | 6.6 mm (±1.4) | Super Bulky / Jumbo |
| US 13 | 9 mm | 15号 (approx) | 6.6 mm (±2.4) | Super Bulky / Jumbo |
| US 15 | 10 mm | 15号 (approx) | 6.6 mm (±3.4) | Super Bulky / Jumbo |
| US 17 | 12 mm | 15号 (approx) | 6.6 mm (±5.4) | Super Bulky / Jumbo |
| US 19 | 15 mm | 15号 (approx) | 6.6 mm (±8.4) | Super Bulky / Jumbo |
| US 35 | 19 mm | 15号 (approx) | 6.6 mm (±12.4) | Super Bulky / Jumbo |
| US 36 | 20 mm | 15号 (approx) | 6.6 mm (±13.4) | Super Bulky / Jumbo |
| US 50 | 25 mm | 15号 (approx) | 6.6 mm (±18.4) | Super Bulky / Jumbo |
Why Most US Sizes Have No Exact Japanese Match
The Japanese JIS needle scale uses increments of approximately 0.3 mm, starting at 0号 (2.0 mm). US sizes were set at different millimeter values that often fall between Japanese sizes. For example:
US size 6 = 4.0 mm. Japanese sizes near 4.0 mm are 7号 (3.9 mm) and 8号 (4.2 mm). Neither is exactly 4.0 mm — so there is no perfect Japanese equivalent of US 6.
In practice, you have two options: use the nearest Japanese 号 size and swatch, or use a metric 4.0 mm needle (which exists as a standard size in many brands) regardless of the 号 numbering.