Hook size

4.5 mm crochet hook

A 4.5 mm crochet hook equals US size 7 and has old UK size 7. It is the recommended hook range for fine (2) and light (3) yarn, and crocheters typically choose it for DK garments, lightweight tops and cotton market bags. Always check gauge with a swatch, because tension varies between crocheters.

By the crochetpatterns.io editorial team · Updated September 20, 2026 · Editorial policy

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4.5 mm crochet hook conversions
Metric	US	Old UK	Suits yarn weights
4.5 mm	7	7	#2 Fine, #3 Light

What is a 4.5 mm crochet hook in US and UK sizes?

A 4.5 mm hook is US size 7 and old UK size 7. Metric millimetres are the only measurement that is the same on every brand, so check the mm size stamped on the hook.

Hook sizes around 4.5 mm
Metric	US	Old UK	Yarn weights
3.75 mm	F-5	—	#2
4 mm	G-6	8	#2
4.5 mm (this hook)	7	7	#2, #3
5 mm	H-8	6	#3
5.5 mm	I-9	5	#3, #4

What yarn weight goes with a 4.5 mm hook?

A 4.5 mm hook is typically used with fine (#2) yarn or light (#3) yarn. Fine yarn gives about 16–20 sc per 4 in / 10 cm and suits baby blankets, summer tops, lightweight cardigans. Light yarn gives about 12–17 sc per 4 in / 10 cm and suits garments, baby items, amigurumi.

Yarn weights for a 4.5 mm hook
Weight	Also called	Crochet gauge	Recommended hooks
#2 Fine	Sport, Baby, 4-ply (UK/AU, approximate)	16–20 sc per 4 in / 10 cm	3.5–4.5 mm
#3 Light	DK, Double knitting, Light worsted, 8-ply (AU/NZ)	12–17 sc per 4 in / 10 cm	4.5–5.5 mm

What can you make with a 4.5 mm hook?

32 patterns in our library use a 4.5 mm hook, including crocheted hot water bottle cover (1915), crocheted hot water bottle cover (1916), crocheted round pillow in three shades (1916), crocheted thumbless mitten (1916), heat-safe double thickness crochet pot holder, quick round crochet coaster in cotton.

Sources and scope

Craft Yarn Council: Hooks & Needles
Reference for metric and US hook sizes. Letter and number labels vary between manufacturers; check the millimetre measurement. Old UK sizes are a separate historical convention.
Craft Yarn Council: Standard Yarn Weight System
Source for categories 0–7 and the crochet gauge and hook ranges. These are starting guidelines; use the gauge in your pattern. Regional ply names and yards per 100 g are approximate comparisons, not CYC specifications.