Look up entries in the included knitting-needle and crochet-hook size tables; confirm metric diameter and current manufacturer labeling.
Search the included knitting-needle and crochet-hook size entries by their displayed system or metric diameter.
Using the needle and hook reference
Search the included knitting-needle and crochet-hook size entries by their displayed system or metric diameter.
Scope of this tool
A matching size label does not establish suitable gauge, fabric, or fit. An empty table cell means no corresponding entry is supplied. A Japanese size is not interchangeable with the same US number.
Method and reference
This is a table lookup, not a numerical conversion formula. Japanese knitting-needle rows follow the cited Clover chart; metric diameter is the basis for comparison. Label conventions can differ by manufacturer.
What is this?
A size converter for knitting needles and crochet hooks that translates between US, metric (mm), UK, and Japanese sizing systems instantly.
Who needs it?
Knitters and crocheters working from international patterns, or anyone whose pattern calls for a needle or hook size in an unfamiliar system.
Bottom line
Select or type any needle or hook size and see the equivalent in every major sizing system, no more guessing whether a 4.0 mm hook is a US G/6.
Needle and Hook Size Converter
How to Convert Needle Sizes
Needle Size Conversion Results
Type any size, metric, US number, UK, or Japanese, to find all equivalents. Try "8" or "5mm".
Metric (mm)
US
UK (old)
Japanese
Yarn Weight
Size
2 mm
US 0
14
–
Lace
2.1 mm
–
–
JP 0
Check yarn label and swatch
2.25 mm
US 1
13
–
Lace / Fingering
2.4 mm
–
–
JP 1
Check yarn label and swatch
2.5 mm
US 1.5
–
–
Fingering
2.7 mm
–
–
JP 2
Check yarn label and swatch
2.75 mm
US 2
12
–
Fingering
3 mm
US 2.5
11
JP 3
Fingering / Sport
3.25 mm
US 3
10
–
Sport / DK
3.3 mm
–
–
JP 4
Check yarn label and swatch
3.5 mm
US 4
–
–
DK
3.6 mm
–
–
JP 5
Check yarn label and swatch
3.75 mm
US 5
9
–
DK
3.9 mm
–
–
JP 6
Check yarn label and swatch
4 mm
US 6
8
–
DK / Worsted
4.2 mm
–
–
JP 7
Check yarn label and swatch
4.5 mm
US 7
7
JP 8
Worsted
4.8 mm
–
–
JP 9
Check yarn label and swatch
5 mm
US 8
6
–
Worsted / Aran
5.1 mm
–
–
JP 10
Check yarn label and swatch
5.4 mm
–
–
JP 11
Check yarn label and swatch
5.5 mm
US 9
5
–
Aran
5.7 mm
–
–
JP 12
Check yarn label and swatch
6 mm
US 10
4
JP 13
Aran / Bulky
6.3 mm
–
–
JP 14
Check yarn label and swatch
6.5 mm
US 10.5
3
–
Bulky
6.6 mm
–
–
JP 15
Check yarn label and swatch
7 mm
–
2
–
Bulky
7.5 mm
–
1
–
Bulky
8 mm
US 11
0
–
Bulky / Super Bulky
9 mm
US 13
–
–
Super Bulky
10 mm
US 15
–
–
Super Bulky
12.75 mm
US 17
–
–
Jumbo
15 mm
US 19
–
–
Jumbo
19 mm
US 35
–
–
Jumbo
25 mm
US 50
–
–
Jumbo
US sizes: Craft Yarn Council. Old UK needles through 8mm: KnitPro. Japanese diameters: Clover needle chart. Size labels vary by manufacturer; use the marked millimetres. A dash means no verified exact equivalent in this table. UK/Canadian hook mappings and conflicting large old-UK needle labels are not supplied.
💡 Quick Reference
Metric (mm) is the universal standard, when in doubt, go by mm.
UK old sizes run backwards, UK 14 is 2mm. Conflicting legacy entries are not supplied.
Japanese sizes start at 0 (2.1mm); size 15 is 6.6mm. Common in Japanese knitting books.
Crochet hooks use both letters and numbers in the US, patterns may use either.
How do I read a knitting needle conversion chart?
Conversion charts list needle sizes in one column and their metric equivalents in another. Most charts show US sizes, metric millimeters, UK sizes, and sometimes Japanese needle sizes all together. One US 8 needle is 5.0 mm, so you can match any size across systems instantly.
Knitting needles have been numbered differently in each country for over a century. The US system uses numbers like 1, 2, and 8. The metric system measures in millimeters from the needle shaft thickness. The UK system uses older numbers that do not match US numbers at all. Japan has its own sizing too. When you find a pattern from another country, the needle size listed will be in that country’s system.
The good news is the actual needle thickness is the same no matter where it was made. A 5.0 mm needle knits the same whether you call it a US 8, a UK 6, or buy it from Japan. So if you look up the metric size, you can find the US equivalent in your hand. Keeping a conversion chart handy or bookmarking one online saves time every time you work with a new pattern.
What is the difference between straight needles and circular needles for sizing?
Straight needles and circular needles use the exact same sizing systems. A US 6 straight needle is 4.0 mm thick, and a US 6 circular needle is also 4.0 mm thick. The shaft diameter is what the size refers to, not the needle length or cable style.
Many knitters think needle size only describes straight needles, but it actually describes the working end of any needle type. Circular needles connect two needle tips with a flexible cable. Interchangeable needles come as tips and cables you buy separately. Double-pointed needles are tiny straight needles in sets of 4 or 5. No matter the shape, the US, metric, UK, and Japanese size numbers all refer to how thick the needle shaft is.
This matters because a pattern tells you the needle size but not always the type. If a pattern calls for US 6 needles, you can use US 6 straights, US 6 circulars, or US 6 double-pointed needles, and the gauge will be the same. The cable length on a circular needle does not change the size number. You choose the needle type for comfort and the stitch count, but the sizing conversion is identical across all needle styles.
How to use it
Select knitting needles or crochet hooks and search a size such as 5mm.
Read the actual metric diameter on the product and check it against the pattern.
Read the result
A matching size label does not establish suitable gauge, fabric, or fit. An empty table cell means no corresponding entry is supplied. A Japanese size is not interchangeable with the same US number.
Check before using the result
✓Follow the exact pattern and product instructions.
✓Make a representative swatch or sample when fit, dimensions, or material behavior matters.
Worked Example
US 8 knitting needles are 5.0 mm in the included table. Clover Japanese knitting-needle size 8 is 4.5 mm. These are different diameters despite sharing the number 8.
Are US, UK, and Japanese size numbers interchangeable?
No. They are different numbering systems. Compare the metric diameter and check the exact product labeling.
How does the converter find a size?
It searches the included table entries. It does not extrapolate an unknown size or identify every historical or manufacturer-specific convention.
Can I use the suggested diameter without swatching?
Use the pattern and product guidance as a starting point, then make a representative swatch. Matching the diameter alone does not guarantee gauge or fit.
What does a blank conversion mean?
No equivalent is supplied in that row. It does not mean a size is zero or universally unavailable.
🧶
Keep your place while you work
Use the FiberTools stitch counter for rows, rounds, repeats, and local project notes.