You can hold the crochet hook against a ruler with mm's shown on it and then look at a gauge that corresponds.
My knitting needle gauge has crochet hooks also listed. In England you have different numbers but the mm's don't change, they are universal in any language. Your patterns mention the mm of a needle or hook as well as the number of the country the pattern came from. Write down the mm and size that you determine for future reference.
My knitting needle gauge has crochet hooks also listed. In England you have different numbers but the mm's don't change, they are universal in any language. Your patterns mention the mm of a needle or hook as well as the number of the country the pattern came from. Write down the mm and size that you determine for future reference.