Labels list the length (yards/meters) and skein weight (g/oz). When in doubt, buy an extra skein—especially for garments and blankets. “Weight” refers to the yarn's thickness—not its grams or ounces. Fingering / Sock – Lightweight, used in socks, lightweight sweaters, and delicate accessories. Sport – A. This tool helps you calculate how much yarn you have in a partial skein or estimate yardage needed for a project. For the most accurate results, use the specific yardage information from your yarn label if. The complete guide to comparing yarn systems — convert Wraps Per Inch (WPI) to US weights, UK Ply, and recommended needle sizes. Select by name or enter your WPI to get full needle & gauge data instantly. The most common way to measure a strand's diameter is with a method called wraps per inch, or WPI.