20 mm crochet hook

A 20 mm crochet hook is not lettered the same way by everyone — it is sold by its millimeter measurement. It is one of the jumbo hooks — the ones for arm-sized yarn, rope and rag strips.

What yarn this hook is for

20 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: Sold as an S by addi and several jumbo sellers, while Boye and the Craft Yarn Council put S at 19 mm. A 20 mm hook often carries no letter at all.

The sizes either side

• One size down: S — 19 mm
• One size up: T/U/X — 25 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 →