4.25 mm crochet hook

A 4.25 mm crochet hook is not lettered the same way by everyone — it is sold by its millimeter measurement. You will meet it in European patterns and in hook sets that fill the gaps between the lettered sizes.

What yarn this hook is for

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

• Fine (2) — also sold as Sport, Baby. Expect about 16–20 single crochet 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.” Only E (3.5 mm) and H (5 mm) mean the same thing at every brand — a hook stamped G is 4 mm from Susan Bates or Clover and 4.25 mm from Boye, and from L upward the letters drift far enough that the Council stops printing single ones.

This size in particular: Boye sells this size as a G. Most other brands (Susan Bates, Clover, Furls) put G at 4 mm, so a G hook is one of two sizes depending on who made it.

The sizes either side

• One size down: G-6 — 4 mm
• One size up: 7 — 4.5 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 →