Knitting Needle Sizes: US, mm & Old UK Chart

Q: What size is a US 8 knitting needle in mm?

US 8 is 5 mm, old UK and Canadian size 6.

Q: What mm is a size 6 knitting needle?

US 6 is 4 mm. An old UK or Canadian size 6 is 5 mm, so check which system the pattern uses.

Q: What is a US 10 needle in mm?

US 10 is 6 mm (old UK 4). US 10 1/2 is 6.5 mm.

Knitting needle sizes, US, metric and old UK

Knitting needle sizes in millimetres, US and old UK and Canadian numbers
Millimetres	US	Old UK and Canadian
1.5 mm	000	none
1.75 mm	00	none
2 mm	0	14
2.25 mm	1	13
2.75 mm	2	12
3 mm	none	11
3.125 mm	3	none
3.25 mm	3	10
3.5 mm	4	none
3.75 mm	5	9
4 mm	6	8
4.25 mm	6	none
4.5 mm	7	7
5 mm	8	6
5.25 mm	9	none
5.5 mm	9	5
5.75 mm	10	none
6 mm	10	4
6.5 mm	10 1/2	3
7 mm	none	2
7.5 mm	none	1
8 mm	11	0
9 mm	13	00
10 mm	15	000
12.5 mm	17	none
12.75 mm	17	none
15 mm	19	none
19 mm	35	none
25 mm	50	none
35 mm	70	none

Two rows share a US number (3.125 and 3.25 mm are both US 3) because brands differ. Buy by millimetres.

Which needle for which yarn

Recommended needle by yarn weight
Yarn weight	Needle, mm	Needle, US	Stockinette per 4 in
0 Lace	1.5 to 2.25 mm	000 to 1	33 to 40
1 Super Fine	2.25 to 3.25 mm	1 to 3	27 to 32
2 Fine	3.25 to 3.75 mm	3 to 5	23 to 26
3 Light	3.75 to 4.5 mm	5 to 7	21 to 24
4 Medium	4.5 to 5.5 mm	7 to 9	16 to 20
5 Bulky	5.5 to 8 mm	9 to 11	12 to 15
6 Super Bulky	8 to 12.75 mm	11 to 17	7 to 11
7 Jumbo	12.75 mm and larger	17 and larger	6 and fewer

Reading a vintage Canadian pattern

Older Canadian and British patterns use the imperial wire gauge numbers in the third column. A pattern asking for "No. 8 needles" means 4 mm, which is a US 6, not a US 8.

Sources

Craft Yarn Council, Hooks & Needles and Standard Yarn Weight System: millimetres, US sizes, needles by yarn weight. https://www.craftyarncouncil.com/standards/hooks-and-needles
Vogue Knitting, Knitting Needle Conversion Chart: old UK sizes. https://www.vogueknitting.com/pattern-help/how-to/techniques-abbreviations/knitting-needles

Common questions

What size is a US 8 knitting needle in mm?

US 8 is 5 mm, old UK and Canadian size 6.

What mm is a size 6 knitting needle?

US 6 is 4 mm. An old UK or Canadian size 6 is 5 mm, so check which system the pattern uses.

What is a US 10 needle in mm?

US 10 is 6 mm (old UK 4). US 10 1/2 is 6.5 mm.

Why are old Canadian needle sizes backwards?

Old UK and Canadian numbers count down as needles get thicker, so 14 is 2 mm and 000 is 10 mm. Vintage Canadian patterns use them.

What needles for worsted weight yarn?

The Craft Yarn Council recommends 4.5 to 5.5 mm (US 7 to 9) for medium weight 4 yarn.

Is there a US size for 3 mm or 7 mm needles?

No. 3 mm and 7 mm have no US number, which is why many patterns give millimetres too.