WPI & mystery yarn identifier

1 Measure your mystery yarn

Wraps per inch Weigh a sample

Wraps per inch (WPI)

Wrap the yarn snugly around a ruler or pencil, side by side without gaps or stretching, and count the wraps in 1 inch (2.54 cm).

Whole ball on the scale (g, optional)

2 Strand structure & fiber feel Structure (optional)

Yarns with the same feel are ranked first, and fibers that distort the WPI reading get a warning.

CYC category: #4 Medium
Technical name: Worsted · Aran · Afghan
Crochet hook: 5.5–6.5 mm (US I-9 – K-10½)
Base gauge 10 × 10 cm: 11–14 single crochet

Your measurement	10 wraps per inch
Estimated linear density	≈ 170 m / 100 g · 186 yd / 100 g
Tex · metric count	≈ 588.2 tex · Nm 1.7
Official CYC WPI range	9–12 WPI
Regional names	Worsted (US) / Aran (UK) / 10-ply (AU/NZ)

Closest Commercial Yarn Matches

Lion Brand 24/7 Cotton100 % density match
#4 Medium · 170 m / 100 g · 170 m per 100 g ball
Lion Brand Basic Stitch Anti-Pilling100 % density match
#4 Medium · 170 m / 100 g · 170 m per 100 g ball
Paintbox Yarns Cotton Aran100 % density match
#4 Medium · 170 m / 100 g · 85 m per 50 g ball
Rico Design Creative Cotton Aran100 % density match
#4 Medium · 170 m / 100 g · 85 m per 50 g ball
Scheepjes Cahlista100 % density match
#4 Medium · 170 m / 100 g · 85 m per 50 g ball

Assumptions: the official CYC WPI ranges overlap, so we assign one category with intermediate cut-offs (above 30, 18.5, 14.5, 11.5, 8.5, 6.5 and 4.5 WPI); density cut-offs are the geometric means of our calculator’s reference densities (800, 400, 300, 230, 170, 110, 65 and 25 m per 100 g), and WPI is converted to density by interpolating between them. Sources: Craft Yarn Council (Standard Yarn Weight System, Wraps Per Inch) and ISO 1144 (tex).