Yarn weight #4

What is worsted weight yarn? Medium (#4) yarn explained

Worsted weight yarn is a medium yarn, category 4 in the Craft Yarn Council system, which also covers slightly thicker aran and afghan yarns. Crocheters work worsted yarn with a 5.5–6.5 mm hook, US I-9 to K-10½, at 11–14 single crochet per 4 inches. It is the most common yarn for blankets and beginners.

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

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Medium yarn at a glance
Detail	Value
CYC number	#4
Also called	Worsted, Afghan, Aran, 10-ply (AU/NZ)
Crochet gauge	11–14 sc per 4 in / 10 cm
Hook size (mm)	5.5–6.5 mm
Hook size (US)	I-9 to K-10½
Yards per 100 g	about 150–220 yd
Best for	Blankets and afghans, Beanies, Granny squares, Beginner projects

What is medium weight yarn called in the US and UK?

Medium yarn is category 4 in the Craft Yarn Council system. You will also see it sold as worsted, afghan, aran, 10-ply (au/nz). It typically runs about 150–220 yd per 100 g, though the exact length depends on the fibre.

How does medium yarn compare with the weights either side?

Light (#3) is one step finer and works up at 12–17 sc per 4 in / 10 cm. Bulky (#5) is one step thicker at 8–11 sc per 4 in / 10 cm. Moving one weight up usually means going up about one to two hook sizes.

Medium yarn and neighbouring weights
Weight	Crochet gauge (4 in)	Hook (mm)	Hook (US)	Yards per 100 g
#3 Light	12–17 sc per 4 in / 10 cm	4.5–5.5 mm	7 to I-9	about 200–280 yd
#4 Medium	11–14 sc per 4 in / 10 cm	5.5–6.5 mm	I-9 to K-10½	about 150–220 yd
#5 Bulky	8–11 sc per 4 in / 10 cm	6.5–9 mm	K-10½ to M-13	about 80–150 yd

What hook size should you use for medium yarn?

Start with a hook between 5.5–6.5 mm (I-9 to K-10½). Standard hooks in that range are 5.5 mm (US I-9), 6 mm (US J-10), 6.5 mm (US K-10½). Go down a size for tighter fabric such as amigurumi, and up a size for drape.

What is medium yarn best for?

Medium yarn is a good choice for blankets and afghans, beanies, granny squares, beginner projects. Our library has 123 patterns in this weight, such as round amigurumi cat for beginners, little round amigurumi bunny with long ears, child's tam o'shanter, 10 to 12 years (1920), classic granny square, simple crochet leaf with stem.

Is aran weight yarn the same as worsted?

Aran and worsted are both medium (#4) yarns, but aran is usually a little thicker. Aran is the common name in the UK and Ireland, and worsted is the common name in the US. Many patterns accept either: make a gauge swatch, because aran yarn makes slightly larger stitches with the same hook, and change hook size until your gauge matches the pattern.

Why is it called worsted weight yarn?

Worsted originally described a spinning method, in which long, combed wool fibres are spun smooth and strong, named after the English village of Worstead. In yarn labels today, worsted weight simply means the medium (#4) thickness, whatever the fibre or spinning method.

Sources and scope

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.