Yarn weights & hook sizes

I don't know about you but I get royally frustrated with yarn weights quoted on patterns, I make an "educated guess" as to the correct weight and quite often end up getting it very wrong - which can be costly.  The patterns state to check the gauge first (which I highly recommend) but to check the gauge you need to have already purchased your yarn and given that a  lot of patterns simply refer to a yarn category rather than a particular yarn you need some information so you can make the best choice.

There are 7 categories of yarn, I've listed them below with their closest UK type and also the hook size that is usually used with the yarn category.

To add to the confusion the hook size and the knitting needle size are often different for a yarn ... and usually the yarn band only states the knitting needle size (what is this crocheter discrimination ???!!!)

I have tried to put all the information that you would need to "calculate" the correct yarn in the table below.


Here is a handy PDF file containing all of these conversions and more Conversions

Symbol	US Type	Ply	UK type	hook size (mm)	Needle Size (mm)	Wraps Per Inch
	Thread, cobweb, lace, fingering	1 -3 Ply	10 count thread	1.4 - 1.6	1.5 -2.25	18 +
	Fingering, stocking, baby	3 - 4 Ply	3-4 Ply	2.25 - 3.5	2.25 - 3.25	14
	Sport	5 Ply	Light DK	3.5 - 4.5	3.25 - 3.75	12
	DK, Light Worsted	8 Ply	DK	4.5 - 5.5	3.75 - 4.5	11
	Worsted, Aran	10 Ply	Aran	5.5 - 6.5	4.5 - 5.5	8 or 9
	Bulky	12 Ply	Chunky	6.5 - 9	5.5 - 8	7
	Super Bulky, Roving		Super Chunky	9  and larger	8 and larger	5 or 6

I've included the wraps per inch (WPI) measurement, you can use this where you don't have the yarn band anymore or if you are recycling old jumpers etc.

To measure the WPI you need a pencil or pen and a ruler or measuring tape.   I find it easier if you cut a nick into the top of the pencil to hold the yarn tight, then just wrap the yarn around the pencil until you have covered 1 inch - using your ruler or measuring tape to measure.

When you have covered exactly 1 inch count the wraps (in the image below 13) and that is your WPI.  You may find that the WPI doesn't match a yarn type exactly but you will get a reasonable understanding of the yarn type you have.

Then comes the question of hook sizes, clearly it would be too simple to have a standard :)

There are metric, US and old UK sizes.  Rather confusingly there is a cross over between the steel (or thread) hooks and the plastic hooks in sizes.  I've split them out to (hopefully) aid clarity.

Here are the conversions;

Steel/Thread Hooks

Metric (mm)	US	UK
0.60	14	6
0.70	13	-
0.75	12	5
0.80	11	-
1.00	10	4
1.25	8	3.5
1.50	7	2.5
1.75	6	2
2.00	1	1
2.50	0	0
3.00	00	2

Plastic Hooks

Metric (mm)	US	UK
2.00	-	14
2.25	B/1	13
2.50	-	12
2.75	C/2	-
3.00	-	11
3.25	D/3	10
3.50	E/4	9
3.75	F/5	-
4.00	G/6	8
4.50	7	7
5.00	H/8	6
5.50	I/9	5
6.00	J/10	4
6.50	K/10.5	3
7.00	-	2
8.00	L/11	0
9.00	M/N-13	00
10.00	N/P-15	000
12.00	O-16	000
15.00	P/Q	-
16.00	Q	-
19.00	S	-

Another link to that conversions file.