Sometimes, you’ll see yarn weight referred to numerically instead of descriptively — is it a 4/8 yarn or DK weight? Well, it could be both! The Craft Yarn Council of America’s Yarn Weight System is sometimes less than helpful if you’re dealing with a yarn not usually used for handknitting. Try this at your next fibery gathering: give everyone the exact same yarn, and I mean from the same skein, along with the exact same size and brand of needles. Knit swatches. Check them against the chart. Ok, now tell me, is Cascade 220 a CYCA #3 (“DK, Light Worsted”) or #4 (“Worsted, Afghan, Aran”)? Sigh.
Sometimes if you’re aiming for real descriptive precision, or if you’re knitting with yarns that are more generally used by weavers, you may run into the “nm” conventions in your yarn shopping. (WEBS and Habu are two places you’ll frequently see this used to describe yarn weights — for example, 2/14 Alpaca Silk, or this 2/10 silk yarn)
Here’s how the nm system works:
One nm equals 1,000 meters of yarn per kilogram (1,000 m/kg), no matter what (whether it’s wool or bamboo — it’s a constant). This equals 50 meters per 50 grams. A 1/8 nm yarn(usually just called “1/8,” without the nm) tells you that the yarn has been spun 8 times longer than the standard, and is therefore finer. You will get 8,000 meters per kilogram if your yarn is a “1/8.”
The first number in the name, or the “1” in “1/8” indicates the number of plies in the yarn. A “1/8” yarn has one ply, a “2/8” yarn has 2 plies, etc.
Here’s where it gets tricky: a “2/8” yarn indicates the yarn was spun to 8,000 meters per kilogram, but then plied into a two-ply yarn. The finished yarn will therefore measure 4,000 meters per kilogram. A “3/8” yarn will have 2,666 meters/kilogram, or 8000 divided by 3.
How does the general numeric system compare to the CYCA chart? From thick to thin:
4/8 yarn yields 1,120 yards per pound and is closest to what handknitters consider a DK weight yarn.
3/8 yarn yields 1,490 yards per pound, or “sport weight” yarn. Similar to a DK weight, but slightly thinner.
2/8 yarn yields 2,240 yards per pound, for a fingering weight yarn.
2/18 yarn yields 5,040 yards per pound, and is considered laceweight.
2/20 yarn yields 5,600 yards per pound, and is also considered laceweight. The difference between 2/18 and 2/20 is slight for a handknitter, akin to the difference between 4/8 and 3/8.
2/24 yarn yields 5,960 yards per pound, and again, is considered laceweight. (Really, what else are you going to do with something that thin? Unless you’re one of those US size triple-0 Sock People. You know who you are).
Hopefully this will help you when shopping for yarn online that isn’t labeled in the way you’re used to, because I’m nothing if not a serious enabler!