S crochet hook: S is 19 mm

A US size S crochet hook is 19 mm at most brands. Turned around: a hook stamped 19 mm is usually sold as an S.

The letter and the number are one hook, not two — “S” is a single size. Older hooks often print only one of the pair, which is most of the confusion. The millimeter is stamped on the hook itself, so when a pattern and a label disagree, trust the mm.

What yarn this hook is for

19 mm falls in the hook range the Craft Yarn Council suggests for one yarn weight — guidelines, in their own words, not rules:

• Jumbo (7) — also sold as Jumbo, Roving. Expect 6 single crochet or fewer to 4 inches.

Before you trust the letter

The Craft Yarn Council puts it plainly: “Because letter and number sizing vary from company to company, rely on the package millimeter (mm) sizing, which is an accurate measurement.” A hook stamped G is 4 mm from Susan Bates or Clover, 4.25 mm from Boye and 4.5 mm from addi — three real hooks, one letter. From L upward they drift far enough that the Council stops printing single letters at all.

This size in particular: Boye and the Craft Yarn Council put S at 19 mm; addi and some jumbo sellers put S at 20 mm. Two real hooks, one letter.

The sizes either side

• One size down: Q — 16 mm
• One size up: 20 mm

Half a millimeter is enough to change how a finished piece comes out. If your gauge is off, this is the dial to turn before you change anything in the pattern — the gauge calculator says which way to go.

See every hook size in one chart →