4 mm crochet hook

The short answer

A 4 mm hook is a US size G/6, UK 8, and 7/0号 in Japan. Buy by the millimetre number — it's printed on every hook and it means the same thing everywhere.

Shaft widths drawn at roughly life size. Hold your hook against the screen — the highlighted bar is 4 mm. Screen scaling varies by device, so treat this as a sanity check, not a measurement.

DK to light worsted, the most common all-round hook.

The same hook in every system

Millimetres (the one that always works)	4 mm
US	G/6
UK	8
Japanese 号	7/0号
Type	standard

Yarn weights that suit this hook

1 standard yarn weight list 4 mm inside their recommended hook range. Expected single crochet gauge over 4 inches is shown as a range — the CYC figures assume a mid-range hook, so at 4 mm you will land toward the loose end. Swatch before you commit.

US weight	UK	Japan	sc / 4 in
Fine	5 ply	中細	16-20

4 mm hooks

Aluminium, ergonomic and Japanese-style options in this size.

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Nearby sizes

3.75 mm 3.5 mm 4.5 mm 3.25 mm 3 mm

All hook sizes · US to Japanese hook chart

Last updated 2026-08-30.