Knitting Needle Size Chart: US, UK & Metric Conversion
Quick answer: US size 7 = 4.5 mm = UK 7. US size 8 = 5.0 mm = UK 6. The full conversion chart below covers every size from US 0 (2.0 mm) to US 50 (25.0 mm). Note that US and UK numbering run in opposite directions — higher US numbers mean bigger needles, higher UK numbers mean smaller ones. Need help matching needles to yarn? Use the needle size calculator.
I own four sets of US 8 needles and zero US 6 needles because I could never remember which metric size I actually needed when shopping in stores that only label in millimeters. That's $60 in duplicate bamboo sitting in a drawer.
The problem is three competing systems. The US uses arbitrary numbers. The UK uses different arbitrary numbers that go in the opposite direction. Metric uses millimeters, which is logical but not what's printed on most American patterns. This chart sorts it out.
Complete Needle Size Conversion Chart
This covers every standard needle size you'll encounter. The metric measurement is the actual diameter of the needle in millimeters — it's the only universal standard, so when in doubt, measure your needle with a gauge tool.
| US Size | Metric (mm) | UK/Canadian | Recommended Yarn Weight |
|---|---|---|---|
| 0 | 2.0 | 14 | Lace (#0) |
| 1 | 2.25 | 13 | Lace (#0), Fingering (#1) |
| 1.5 | 2.5 | — | Fingering (#1) |
| 2 | 2.75 | 12 | Fingering (#1) |
| 3 | 3.25 | 10 | Fingering (#1), Sport (#2) |
| 4 | 3.5 | — | Sport (#2) |
| 5 | 3.75 | 9 | DK (#3) |
| 6 | 4.0 | 8 | DK (#3), Worsted (#4) |
| 7 | 4.5 | 7 | Worsted (#4) |
| 8 | 5.0 | 6 | Worsted (#4) |
| 9 | 5.5 | 5 | Worsted (#4), Bulky (#5) |
| 10 | 6.0 | 4 | Bulky (#5) |
| 10.5 | 6.5 | 3 | Bulky (#5) |
| 11 | 8.0 | 0 | Bulky (#5), Super Bulky (#6) |
| 13 | 9.0 | 00 | Super Bulky (#6) |
| 15 | 10.0 | 000 | Super Bulky (#6) |
| 17 | 12.75 | — | Super Bulky (#6), Jumbo (#7) |
| 19 | 15.0 | — | Jumbo (#7) |
| 35 | 19.0 | — | Jumbo (#7) |
| 50 | 25.0 | — | Jumbo (#7) |
Also notice that US 11 to US 13 skips 12 entirely. There is no US 12 in the standard system. If someone asks to borrow your "size 12 needles," they probably mean 12 mm, which is between US 15 and US 17.
Why US and UK Sizes Are Opposite
This trips up everyone who buys patterns from both countries. In the US system, bigger numbers mean bigger needles. In the UK system, bigger numbers mean smaller needles.
| Size | US Logic | UK Logic |
|---|---|---|
| Smallest | US 0 (2.0 mm) | UK 14 (2.0 mm) |
| Medium | US 8 (5.0 mm) | UK 6 (5.0 mm) |
| Largest | US 50 (25.0 mm) | UK 000 (no equivalent) |
My rule: always verify the metric size. If the pattern lists "US 8 (5.0 mm)" — great, no ambiguity. If it just says "size 8," check the publication country. British patterns from Rowan, Debbie Bliss, or Sirdar use UK sizing. American patterns from Vogue Knitting, Interweave, or Lion Brand use US sizing.
The safest approach is to buy a needle gauge tool — a small card or ruler with holes for each millimeter size. Stick your needle through until you find the snug fit. The metric measurement never lies.
Needle Types and When to Use Each
Size matters, but so does needle type. Here's a quick breakdown.
Straight needles — the classic two-stick setup. Good for flat pieces: scarves, dishcloths, blanket panels. Limited by length — you can only fit so many stitches on a 14-inch needle. For anything wider than about 24 inches, you'll struggle.
Circular needles — two short needle tips connected by a flexible cable. Use them for knitting in the round (hats, cowls, sleeves) and also for flat knitting on wide pieces. A 32-inch circular can hold a blanket's worth of stitches. I use circulars for 90% of my projects, including flat ones.
Double-pointed needles (DPNs) — sets of 4 or 5 short needles for small circumference knitting. Socks, gloves, hat crowns. Awkward at first, but nothing else handles a 7-inch sock circumference.
Interchangeable sets — circular needle tips that screw onto different cable lengths. One set replaces dozens of fixed circulars. Worth the investment ($50–150) if you knit regularly.
| Project Type | Best Needle Type | Typical Sizes |
|---|---|---|
| Scarf | Straight or circular | US 7–9 (4.5–5.5 mm) |
| Hat | 16" circular + DPNs | US 6–8 (4.0–5.0 mm) |
| Socks | DPNs or 9" circular | US 1–3 (2.25–3.25 mm) |
| Blanket | Long circular (32"+) | US 8–11 (5.0–8.0 mm) |
| Sweater | Circular (various) | US 5–8 (3.75–5.0 mm) |
| Lace shawl | Circular | US 3–6 (3.25–4.0 mm) |
How to Choose the Right Needle Size
The yarn label suggests a needle size. The pattern specifies a needle size. Your gauge swatch determines the needle size you actually use. These three numbers are often different.
Start with the pattern's recommended needle size. Knit a 6-inch gauge swatch in the pattern stitch. Count stitches per 4 inches. If you match the pattern gauge, you're done. If you have too many stitches (fabric too tight), go up a needle size. Too few stitches (fabric too loose), go down.
Most knitters have a personal tendency — tight, loose, or average. I knit tight, so I almost always go up one needle size from the pattern recommendation. After a while, you'll know your tendency and can predict the adjustment before swatching.
If you're not following a pattern and just want a good fabric for your yarn weight, use the recommended needle size from the yarn label. It's printed on every skein inside a small needle icon. That's a solid starting point.
See the full knitting gauge guide for a step-by-step walkthrough of swatching and adjusting.
Needle Material: Does It Matter?
More than you'd think for comfort. Less than you'd think for gauge.
| Material | Grip | Speed | Weight | Best For |
|---|---|---|---|---|
| Bamboo/Wood | High grip | Slower | Light | Slippery yarn, beginners |
| Metal (aluminum) | Low grip | Fast | Medium | Experienced knitters, speed |
| Carbon fiber | Medium grip | Fast | Very light | Long sessions, arthritis |
| Plastic/Acrylic | Medium grip | Medium | Very light | Budget, large sizes |
For larger sizes (US 13+), weight becomes the main factor. Metal US 15 needles are heavy enough to cause wrist fatigue on long projects. Bamboo or plastic in those sizes feels noticeably lighter.
One caveat: cheap bamboo needles can snag and splinter. Brands like ChiaoGoo, Clover, and Knitter's Pride make well-finished bamboo. Dollar-store bamboo needles will give you splinters and a hatred of natural materials.
FAQ
What size knitting needles should a beginner use?
US 8 (5.0 mm) with worsted weight yarn. It's the standard teaching combination — big enough to see your stitches clearly, small enough to create fabric that actually looks knitted. Start with bamboo or wood needles for the extra grip. Avoid anything smaller than US 6 or thinner than DK weight until you're comfortable with the basic stitches.
Can I use different needle sizes than the pattern says?
Yes, but you'll get different gauge and fabric characteristics. Going up a size creates a looser, drapier fabric. Going down creates a tighter, denser fabric. If you're making something where size matters (a sweater, hat, or socks), you must match the pattern's gauge — adjust your needle size until you hit it. For scarves and blankets where exact dimensions are flexible, you can use whatever needles feel good.
What's the difference between US 10 and US 10.5?
US 10 is 6.0 mm and US 10.5 is 6.5 mm. That half-millimeter difference sounds tiny but changes your gauge by roughly 1–2 stitches per 4 inches. For a blanket, that doesn't matter much. For a fitted garment, it can mean an inch of difference across the chest. When a pattern specifies 10 vs 10.5, use what it says.
How do I measure a needle with no size marking?
Use a needle gauge tool — a small flat card with labeled holes. Insert the needle into each hole until you find a snug fit. They cost $3–8 at any yarn shop. Alternatively, measure the diameter with calipers and match it to the metric column in the chart above. Never guess — a half-millimeter error throws off your entire gauge.
Are vintage needle sizes different?
Yes. Pre-1980s American needles used a slightly different system, and some sizes don't match modern equivalents exactly. Old UK aluminum needles are generally consistent with modern UK sizing. If you inherit grandma's needle collection, measure each one with a gauge tool rather than trusting the stamped number. Some vintage needles also have non-standard tip shapes that affect gauge.
Next Steps
- Use the needle size calculator to match needles to your yarn based on the gauge you need.
- Check the yarn weight guide for which yarn weights pair with which needle sizes.
- Read the knitting gauge guide to learn how to swatch properly and adjust needle size for a perfect fit.