Definition
Yarn weight
A category describing how thick a yarn is, published as a numbered system from 0 (lace) to 7 (jumbo) with an equivalent name such as fingering, DK, worsted or bulky. The same yarn can carry different names in different countries: a US worsted is close to a UK aran, and a UK 8 ply is close to a US light or DK.
Yarn weight is only half the story, because the gauge you work at decides the finished fabric. Always match the gauge a pattern asks for rather than the name on the band.
Tools that use this term
Yarn Weight Converter
Convert between the US yarn weight numbers, the UK and Australian ply names, and wraps per inch.
Yarn Calculator
Work out how much yarn a project needs from its finished size, your stitch gauge and the yarn weight you plan to use.
Crochet Hook Size Converter
Convert crochet hook sizes between metric millimetres, US letter sizes and the old UK numbering.