ac conversion chart

Crochet hook size conversions chart

There are a lot of differences in terminology for hook sizes and yarn weights, so we provide you with very convenient diagrams that would easily convert the necessary millimeters to letters. We will show you a conversion chart (it looks like an ac conversion chart to convert square feet to acres and back) which is very useful for all beginners.


Crochet hook sizes differ because they were produced in different countries. The NUMBERS represents us the diameter of shaft (in millimeters – “mm”). This shaft is the part of the hook between the point and handle. In the USA we are using Letter sizes, where “B” size – usually is the smallest, and “S” is the largest.

Crochet Hook Size
  Metric US
2.25 mm B-1
2.75 mm C-2
3.00 mm C-2
3.25 mm D-3
3.50 mm E-4
3.75 mm F-5
4.00 mm G-6
4.50 mm 7
5.00 mm H-8
5.50 mm I-9
6.00 mm J-10
6.50 mm K-10.5
7.00 mm K-10.75
8.00 mm L-11
9.00 mm M-13
10.00 mm N-15
12.00 mm P-16
15.00 mm P/Q
16.00 mm Q
19.00 mm S
20.00 mm S

ac conversion chart

So in the conversion chart we can see that the H crochet hook size chart is equaled to 5mm is marked at number 8 and it does not quite match logically. However, if you look at the conversion, and in the table the hook diagram, you will easily understand everything and start the binding process! The same is for a 9mm crochet hook conversion equals to letter M size, 4mm crochet hook letter is G! Interesting, that 3mm crochet hook letter C-2 is the same as in the hook 2.75 mm (Canada/UK hook size 11 for example), 7mm crochet hook letter equals to letter K/10.75 (Canada/UK hook size 2), 5.5 crochet hook conversion is I-9 and the back conversion for size f crochet hook in mm is 3.75 mm.


The same conversion is used to find out the size of the steel crochet hook. In the Metric system a 0.55 mm hook is the same as 18 sizes of the US. Or US size 10 is proportional to 1.25 mm:

Steel Crochet Hook Size
Metric US
0.50 mm 18
0.60 mm 16
0.75 mm 14
0.85 mm 13
1.00 mm 12
1.10 mm 11
1.25 mm 10
1.50 mm 8
1.65 mm 7
1.75 mm 6
1.90 mm 5
2.00 mm 4


Of course, you could need to have a Yarn Weights and Required Hook Sizes, if you don’t be confused if you meet some different materials for knitting, which you can find in the next chart:

Yarn Weights and Required Hook Sizes
UK US AUS Hook Size
Lace 1 Ply 2 Ply 1.50-2.25 mm
Fingering 2 Ply 3 Ply 2.25-3.50 mm
Sport 4 Ply 5 Ply 3.50-4.50 mm
DK DK 8 Ply 4.50-5.50 mm
Worsted Aran 10 Ply 5.50-6.50 mm
Chunky Bulky 12 Ply 6.50-9.00 mm
Super Chunky Super Bulky 14 Ply 9.00 mm (and above)

As you can see, for a hook size 1.50mm-2.25mm in the USA you should use a 1 Ply Yarn weight for knitting, in Australia – 2 Ply, and for the United Kingdom you should choose LACE weight of the yarn.

We have some differences not only in sizes and weights systems. Some crochet terminology have small, but powerful distinctions, like DOUBLE CROCHET in British terminology, becomes a SINGLE CROCHET in USA terminology:


Crochet Terminology
British US
Double Crochet Single Crochet
Treble Double Crochet
Half Treble Half Double Crochet
Double Treble Treble
Triple Treble Double Treble
Miss Skip

sizes of crochet hooks

So what we got? Know we know about all the differences between most popular sizes and weights systems. You can use our conversions chart to be sure that you have chosen the right size of hook and enjoy the knitting anywhere you can!


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