Yarn Weight Converter

The Yarn Weight Converter maps yarn weight between the US Craft Yarn Council system (numbers 0–7), UK traditional names (Lace, 2-ply, 4-ply, 5-ply / Sport, DK, Aran, Chunky, Super Chunky, Jumbo), Australian/UK ply numbers (2-ply through 16-ply+), and WPI (Wraps Per Inch — measured by wrapping yarn around a ruler). Essential for knitters and crocheters substituting yarn across pattern publishers from different countries, since the same pattern in US, UK, and AU patterns can call for differently-named yarn at the same actual thickness. The US 0–7 system (introduced by Craft Yarn Council circa 2003 to standardize confusing names): 0 Lace (cobweb-thin), 1 Super Fine / Fingering (sock weight), 2 Fine / Sport, 3 Light / DK (Double Knit), 4 Medium / Worsted / Aran, 5 Bulky / Chunky, 6 Super Bulky, 7 Jumbo (arm-knitting thickness). The numerical system is most useful for cross-referencing on yarn labels; the names persist because knitting culture is older than the standardization. UK and AU systems use 'ply' counts referring to historical strand counts in wool yarn. Modern ply isn't literal strand count — 'DK' (Double Knit) used to mean two strands plied together for thicker yarn but now just refers to weight tier. AU 8-ply ≈ UK DK ≈ US 3 Light. AU 10-ply ≈ UK Aran ≈ US 4 Medium / Worsted. The ply system feels arbitrary to new knitters; using US 0–7 numbers is more reliable for cross-referencing. WPI (Wraps Per Inch) is the empirical measurement — wrap yarn snugly but without stretching around a ruler, count wraps in one inch. WPI works for unlabeled yarn (handspun, vintage, found yarn) where you don't have category information. WPI ranges: Lace 30–40, Fingering 14–30, Sport 12–18, DK 11–15, Worsted 9–12, Bulky 7–9, Super Bulky 5–7, Jumbo 1–4. The wide ranges reflect that yarn weight categories are bands, not precise points. WPI within a band defines specific weight.

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1. 1Step 1 — Identify what yarn weight info you have (US number, UK name, AU ply, or just the yarn)
2. 2Step 2 — For unlabeled yarn, measure WPI: wrap yarn snugly around ruler, count wraps in 1 inch
3. 3Step 3 — Select source system and enter your value
4. 4Step 4 — Calculator maps your input to all four equivalent systems
5. 5Step 5 — Use cross-reference to substitute yarn from international patterns
6. 6Step 6 — When substituting, also verify gauge (stitches per 4 inches) — yarns within same weight can vary slightly
7. 7Step 7 — Buy 10% extra when substituting to account for gauge differences

• !Substituting yarn based on yardage alone — weight matters more for gauge
• !Trusting 'Worsted' label without verifying with WPI — different brands' worsteds vary
• !Not swatching before starting fitted garment project
• !Confusing 'ply' with literal strand count (modern ply is weight category, not strands)
• !Buying exact yardage without 10% buffer for substituted yarn