Hook size 'code'

i see that there are J,H, I, etc as hook size’s ‘code’…
but i see sometimes like this: 5/0, 3/0, etc…i really don’t understand the size of that hook (in mm)…i have 6/0 hook and J (or I?) hook (6 mm) but the 6/0 is smaller than that J hook…

does any one know about hook size code?..i looked into some website but mostly they explain about that alphabet hook…

thank you

Its so funny that you brought this up, because I was actually wondering the same thing. I’ve been working with a lot of japanese crochet patterns, and 3/0 etc. is how they display the hook sizes. I finally tracked down one of my friends who went to college in japan to see if he could help me translate, and he found me a site that explained the conversions! I’ll put it all in here for you…

2/0-3/0 2.0-2.3mm US B/1
4/0-6/0 2.5-3.5mm US C/2 D/3 E/4
7/0 4.0mm US G/6
7.5/0-9/0 4.5-5.5mm US 7 H/8 I/9
8/0-10/0 5.5-6.0mm US I/9 J/10

I hope that makes a little bit of sense…

Was going to say that the sizes may vary for international patterns. I know they are different with UK sizes anyway :slight_smile:

japanese crochet?..hahaha…this is so funny, too because i am doing it right now…i got hooked because of japanese crochet books i bought…:cheering:

thanks for the info…this is absolutely helpful

Yes, i found UK’s is different, too…but i can still find the conversion chart…i think it’s available a lot on many webs

Kpixie.com has a handy little pdf chart that lists a size conversion (like what Riss posted) plus a simplified explanation of a typical materials list:


I figured I’d be referring to this pretty often so I have it bookmarked and saved to my computer. :slight_smile:


i’ve printed it and save it on my computer…this link is helpful