Needle Size Conversion
Complete overview of international needle sizes.
Needle Sizes
Needle Size Converter
Easily convert between mm, US, and UK needle sizes.
| mm | US | UK |
|---|---|---|
| 2 | 0 | 14 |
| 2.25 | 1 | 13 |
| 2.5 | – | 12 |
| 2.75 | 2 | 12 |
| 3 | – | 11 |
| 3.25 | 3 | 10 |
| 3.5 | 4 | – |
| 3.75 | 5 | 9 |
| 4 | 6 | 8 |
| 4.5 | 7 | 7 |
| 5 | 8 | 6 |
| 5.5 | 9 | 5 |
| 6 | 10 | 4 |
| 6.5 | 10½ | 3 |
| 7 | – | 2 |
| 7.5 | – | 1 |
| 8 | 11 | 0 |
| 9 | 13 | 00 |
| 10 | 15 | 000 |
| 12 | 17 | – |
| 15 | 19 | – |
| 19 | 35 | – |
| 25 | 50 | – |
Why use a needle size conversion chart?
When knitting patterns from other countries, you will often encounter confusing needle sizes. While metric sizing (2mm, 3mm, 4mm etc.) is standard in Europe, US patterns use a numbered scale (US 0, 1, 2...) and vintage British patterns use a scale that runs in reverse.
A needle size conversion chart is essential when working on English knitting patterns or purchasing needles from international websites. Using the wrong size needle can ruin your project by resulting in an incorrect gauge, causing your garment to end up too big or too small.
How to convert needle sizes manually
Unfortunately, there is no simple mathematical formula to convert between these scales since they are based on historical standards. The best option is to refer to a conversion table.
Common conversions to remember
Here are the most frequently used needle sizes and their equivalents:
- 3.5mm = US 4 – Common for socks and fine garments
- 4mm = US 6 – Standard for many sweaters
- 4.5mm = US 7 – Popular for worsted weight yarn
- 5mm = US 8 – Frequently used for sweaters and scarves
- 6mm = US 10 – For chunky yarn and fast projects
British (UK) sizes
The vintage British system is more complex because the numbers run in reverse compared to the US system. For instance, a UK 8 is 4mm, whereas a UK 6 is 5mm. Fortunately, most modern patterns have adopted metric sizes, but you will still need this conversion for vintage patterns.
Remember that the needle size specified in a pattern is always a suggestion. Your personal tension is what determines the final gauge. Always knit a swatch!
Tips for perfect results
- Always knit a swatch: Even if you use the correct needle size according to the chart, the material of the needles (wood, metal, bamboo) can affect your tension. Metal needles are slippery and often yield a looser gauge, while wood offers more friction for a tighter stitch.
- Check your needles: Older needles may be worn and have a slightly different diameter than marked. If in doubt, measure them using a needle gauge.
- Trust the gauge, not the size: If the pattern states "US 7 or size needed to obtain gauge," obtaining the correct gauge is what matters. Use our gauge calculator to find the right size.
- Save the conversion chart: Bookmark this page or take a screenshot so you always have it handy when buying needles or starting new projects.
- Circular vs. straight needles: Sizing conversions remain the same, but remember that circular needles also specify cable lengths (16", 24", 32" etc.).
What is the difference between US and UK needle sizes?
The US system uses rising numbers (0, 1, 2...) for thicker needles, while the old British system (UK) used falling numbers. Fortunately, most patterns today use the metric system in millimeters (mm).
Is 4mm the same as US size 6?
Yes, a 4mm needle generally corresponds to US size 6. See our complete table for all other sizes.