What are the different American crochet hook sizes?

American crochet hooks have a letter/number combination beginning with "B/1," which is equivalent to a 2.5-millimeter hook. The letters and numbers continue through "S" with some exceptions. For example, a crochet hook in size 7 does not exist. Letter "G" is paired with the number six, and "H" is paired with eight. It is also important to note there is no "R" hook. Additionally, the numbers stop at 16, meaning letters "Q" and "S" each do not have a number.

When using steel hooks to crochet with fine lace or thread, the sizes begin with the smallest, 00, and the next smallest size is 0. The hooks continue in ascending order through size 14. There are no skipped numbers, and this numbering system is standard except for beginning with 00.

Each crochet hook, whether American or European, has a metric equivalent in millimeters to make converting sizes easier. When choosing a crochet hook for an international pattern, looking at the metric equivalent is useful. However, millimeter sizes often vary based on the specific manufacturer. As a result, once a crochet hook is chosen for a pattern, it is important to continue using the same hook throughout the entirety of the pattern.