5mm Knitting Needle Size
A 5mm needle is US 8 and UK 6. It's the single most popular needle size for worsted-weight knitting — more patterns are written for this diameter than any other.
US 8 · UK 6 · Japanese ~10号 · Yarn: Worsted (#4)
Convert Any Needle Size
Open Needle Size Converter →Enter 5mm — or any other size — to see all equivalents side by side.
5mm in Every Sizing System
| System | Size | Notes |
|---|---|---|
| Metric | 5.0 mm | The actual diameter |
| US | 8 | Most popular size in US patterns |
| UK / Australian | 6 | UK 8 is 4.0mm (US 6) — not the same needle |
| Japanese | ~10号 | 10号 = 5.1mm — 0.1mm off, essentially the same |
| Yarn weight | Worsted (#4 Medium) | Standard gauge: 18–20 sts per 4" |
About 5mm Needles
Worsted is the most widely sold yarn weight in the US and Canada, and 5.0mm is the needle that goes with it. European and Australian patterns written for worsted-equivalent yarn will say 5mm rather than US 8, but they're asking for the same thing.
If you're starting out or building a needle collection, a 5mm circular is probably the most useful single needle you can own. It covers the broadest range of beginner patterns, and worsted yarn is the easiest weight to work with.
5mm and the UK system
5.0mm = UK 6. This trips people up because UK 8 is 4.0mm (US 6), not 5.0mm. The UK system runs backwards — higher number means smaller needle. So when a British pattern says "size 6," they mean 5.0mm, i.e., what Americans call US 8.
Japanese 10号
Japanese 10号 is technically 5.1mm, not 5.0mm. The difference is 0.1mm — effectively nothing for most projects. If you're knitting a Japanese pattern calling for 10号, a standard 5.0mm needle will work fine.
What to Knit with 5mm Needles
The worsted range on 5mm is huge. A few examples across project types:
Hats — a standard adult beanie on 16" circulars at US 8 is one of the most common beginner projects for a reason. Fast, practical, and a good way to practice knitting in the round.
Sweaters and cardigans — the majority of adult knitwear patterns in the US are written for worsted on US 7–9, with US 8 being the most common call.
Scarves, cowls, and shawls — straightforward projects that let you focus on stitch patterns. Worsted on 5mm gives a warm, drapey result.
Amigurumi and toys — worsted weight is standard for knitted toys, and 5mm gives a firm enough fabric to stuff without the filling showing through.
Dishcloths and home goods — cotton worsted on 5mm is great for dishcloths, washcloths, and pot holders. Fast to knit and practical.