First off, there are two "types" of needle sizing. The first is the US method of measuring needles, and the second is the UK/Canada method of measuring. Therefore, there are two answers to your question.
For US knitting needles, there are sizes:
0 (2.0 mm)
1 (2.25 mm)
2 (2.75 mm)
3 (3.25 mm)
4 (3.5 mm)
5 (3.75 mm)
6 (4.0 mm)
7 (4.5 mm)
8 (5.0 mm)
9 (5.5 mm)
10 (6.0 mm)
10 1/2 (6.5 mm)
11 (8.0 mm)
13 (9.0 mm)
15 (10.0 mm)
17 (12.0 mm)
19 (16.0 mm)
35 (19.0 mm)
50 (25.0 mm)
For UK/Canada sizes, there are:
14 (2.0 mm)
13 (2.25 mm)
12 (2.75 mm)
11 (3.0 mm)
10 (3.25 mm)
9 (3.75 mm)
8 (4.0 mm)
7 (4.5 mm)
6 (5.0 mm)
5 (5.5 mm)
4 (6.0 mm)
3 (6.5 mm)
2 (7.0 mm)
1 (7.5 mm)
0 (8.0 mm)
00 (9.0 mm)
000 (10.0 mm)
4mm describes the size around (thickness) which is equal to US6. This isn't sized in inches. Length can vary.
This would be a US G or size 6. (UK or Canadian 8).
A 4mm hook is a US size F. Numerically it's size 5 or 6. In Britain it would be size 8.
4.0mm needles are a US 6 or a UK 8.
That would be a G.
3mm is between a US 2 and US 3.
7
4mm is a US size 6.
8
Why?
20mm knitting needles are needles that are 20mm in diameter. They are also known as US size 35 needles.
no
Any store should have knitting needles.
Your answer depends on the yarn you choose for your project.
Broomstick knitting needles are the size of a broomstick handle. That would be approximately 2.75 inches in circumference or about 7/8ths of an inch in diameter. This would be a US 42 size (I believe), or a 22.0 to 22.25mm size, needles.
The ball band on yarn often tells you what size needles it is suitable for.
knitting needles
A 3mm crochet hook is halfway between a C and D size in US sizes.
No, this is an information site, not a business.
it means you have either added yarn overs or dropped stitches. it might mean you are a beginner or it might mean you are knitting lace and want the holes. or that you are knitting on needles slightly larger than you would use for a not holey fabric. P.S.: You are supposed to have holes in your knitting! The hole size is because the size of the needle. (ex: large size needles=large hole, small needle= small hole) Understand now?
I don't know, type it in on wiki answers!