The internet has opened up a whole world (quite literally!) of crochet patterns old & new. I love to source vintage patterns for inspiration in my designs, but often the hook size is in old English or American (as opposed to Metric mm) which would result in the finished item being far from the correct size. This is obviously a problem if you are making a garment!
There is quite a difference between international hook sizes - and stitch definitions too, but more on that later. To make things easy, I have complied a list of the most common hook sizes in Metric, Old English and American for you to use as a reference guide. Some sizes do not have an equivalent so simply use the next size up or down depending on whether you have a tighter or looser tension when you crochet. It is always best to do a swatch check if you are going to be making a garment - I know, the sound of it is super tedious but it beats having to undo a finished item that turned out the wrong size! (believe me, that is no fun at all!)
Metric English American
1 *************** *************** 10
1.25 *************** *************** 8
1.5 *************** *************** 7
1.75 *************** *************** 5
2 *************** 14 *************** B/1
2.25 *************** 13 *************** B/1
2.75 *************** 12 *************** C/2
3 *************** ***************
3.25 *************** 11 *************** D/3
3.5 *************** 10 *************** E/4
3.75 *************** 9 *************** F/5
4 *************** 8 *************** G/6
4.5 *************** 7 *************** 7
5 *************** 6 *************** H/8
5.5 *************** 5 *************** I/9
6 *************** 4 *************** J/10
6.5 *************** 3 *************** 10.25
7 *************** 2 *************** K/10.5
8 *************** 0 *************** L
9 *************** 00 *************** N
10 *************** 000 ***************
12 ***************
15 ***************
20 ***************
As soon as I have worked out how to make a downloadable version of this I will post it here.
Crochet hook photo by Jeremy Wilson