Hook size

3.75 mm crochet hook

A 3.75 mm crochet hook equals US size F-5 and has no old UK number. It is the recommended hook range for fine (2) yarn, and crocheters typically choose it for sport-weight garments, baby blankets and doilies in fine cotton. Always check gauge with a swatch, because tension varies between crocheters.

By the crochetpatterns.io editorial team · Reviewed September 13, 2026 · Editorial policy

3.75 mm crochet hook conversions
Metric	US	Old UK	Suits yarn weights
3.75 mm	F-5	—	#2 Fine

What is a 3.75 mm crochet hook in US and UK sizes?

A 3.75 mm hook is US size F-5 and has no old UK equivalent. 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 3.75 mm
Metric	US	Old UK	Yarn weights
3.25 mm	D-3	10	#1
3.5 mm	E-4	9	#1, #2
3.75 mm (this hook)	F-5	—	#2
4 mm	G-6	8	#2
4.5 mm	7	7	#2, #3

What yarn weight goes with a 3.75 mm hook?

A 3.75 mm hook is typically used with fine (#2) yarn. Fine yarn gives about 16–20 sc per 4 in / 10 cm and suits baby blankets, summer tops, lightweight cardigans.

Yarn weights for a 3.75 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

What can you make with a 3.75 mm hook?

6 patterns in our library use a 3.75 mm hook, including flower afghan (1951), granny afghan (1951), la louisian square shawl (1951), square dance afghan (1951), square dance shawl afghan (1951), waltz hairpin lace cape (1960).