4mm Knitting Needle Size
A 4mm needle is US 6 and UK 8. It's the standard size for DK weight yarn and one of the most useful needles to own.
US 6 · UK 8 · Japanese ~7号 or 8号 · Yarn: DK (#3)
Convert Any Needle Size
Open Needle Size Converter →Enter 4mm — or any other size — to see all equivalents side by side.
4mm in Every Sizing System
| System | Size | Notes |
|---|---|---|
| Metric | 4.0 mm | The actual diameter |
| US | 6 | |
| UK / Australian | 8 | UK 6 is a different needle (5.0mm = US 8) |
| Japanese | ~7号 or 8号 | 7号 = 3.9mm, 8号 = 4.2mm — no exact match |
| Yarn weight | DK (#3 Light) | Standard gauge: 22 sts per 4" |
About 4mm Needles
4.0mm is the standard DK needle size used in most European, British, and Australian patterns. If you buy needles in the UK or Europe they'll be labeled in mm, so "4mm" is simply what the needle says on the side. American patterns will typically write this as US 6.
DK (double knit) is one of the most widely available yarn weights globally — you'll find an enormous range of yarns at this thickness. The 4mm needle produces a balanced fabric with it: not too dense, not too open.
The Japanese gap
4.0mm falls between Japanese 7号 (3.9mm) and 8号 (4.2mm). There's no JIS-standard Japanese needle that's exactly 4.0mm. If you're knitting a Japanese pattern that calls for something in this range, swatch on both and use whichever gives you the right gauge.
UK 8 vs US 8 — still worth saying
UK 8 = 4.0mm = US 6. UK 6 = 5.0mm = US 8. The numbers are swapped. This is the one that catches people out the most, and it's worth double-checking every time you pick up a British or Australian pattern.
What to Knit with 4mm Needles
DK weight everything — baby garments, lightweight sweaters, colorwork, socks in DK, shawls. 4mm DK is one of the most pattern-rich combinations in knitting.
Linen and cotton projects — many linen-blend and cotton yarns are sold as DK weight. 4mm gives a good result with both, though you may need to go up slightly for cotton since it has less stretch.
Fine cables — cable patterns read well at DK weight. The individual cables are delicate enough to layer without the fabric getting too thick.