2.25 mm crochet hook

The short answer

A 2.25 mm hook is a US size B/1, UK 13. 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 2.25 mm. Screen scaling varies by device, so treat this as a sanity check, not a measurement.

Amigurumi, fingering weight, tight fabric.

The same hook in every system

Millimetres (the one that always works)	2.25 mm
US	B/1
UK	13
Japanese 号	no Japanese size
Type	standard

Systems with no exact match

2.25 mm has no direct equivalent in 1 of the three systems. These are the closest hooks, with the size difference spelled out — substitute at your own gauge risk.

System	Closest hook	Actual size	Difference
Japanese	3/0号	2.3 mm	+0.05 mm

Yarn weights that suit this hook

2 standard yarn weights list 2.25 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 2.25 mm you will land toward the loose end. Swatch before you commit.

US weight	UK	Japan	sc / 4 in
Lace	1 ply	極細	32-42
Super Fine	4 ply	合細	21-32

2.25 mm hooks

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

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Nearby sizes

2.3 mm 2 mm 2.5 mm 1.75 mm 2.75 mm

All hook sizes · US to Japanese hook chart

Last updated 2026-08-30.