About this tool

This site exists to answer one question fast: "what does this yarn weight mean in a different system, and what do I substitute it with?" It converts between US, UK, and Australian yarn weight names, shows WPI, gauge, and needle/hook sizes, and — unlike most yarn weight tools — also covers crochet thread numbering (DMC, Lizbeth, and similar) and yardage substitution math.

Every number that comes from an official standard is labeled as such and linked to its source: theCraft Yarn Council's Standard Yarn Weight System. Where a figure is a widely used community convention instead — WPI ranges, UK/AU name equivalents, thread-size matching — we say so plainly, rather than presenting it as official. Yarn gauge always varies by brand and fiber, so treat every number here as a starting point for your swatch, not a substitute for it.