Can someone explain yarn size terminology (eg. 20/2 cotton yarn)?
This is sort of a long round-about answer, but I’ll do the best I can. It’s probably more than you need to know, but I’ll do it anyway.
The numbers represent the size of the yarn and the number of plies. For yarns of cotton and linen, in the USA, the size is given first, followed by the number of plies. The British system places the ply number first followed by the size. Different fibers have different numbering systems. The size number is an indicator of the yards per pound for that particular fiber.
Number 1 cotton, for example, has 840 yards per pound. The yardage per pound increases as the size number increases. That is, there is 840 yards in a standard skein of yarn at this thickness. Consequently, a number 5 cotton will have 5 times the yardage per pound as a number 1 cotton; there are 5 skeins, each 840 yards, that can be spun from a pound of cotton, when the yarn is this thickness — which is much thinner than a count of 1. To calculate the yardage multiply 5 x 840. The answer is 4200; therefore a number 5 cotton contains 4200 yards per pound. A 5/2 yarn is two strands of number 5 cotton plied together. Due to plying the quantity of fiber in one yard has now increased; consequently the yardage per pound will decrease. To figure the yardage, multiply the size number by 840 as above, and divide by the number of plies. 5 x 840 = 4200. 4200 divided by 2 = 2400. The 5/2 cotton contains 2400 yards per pound. Since the original measurement is done on a single strand of yarn, and plying takes away some of that length, estimate about 5% loss due to plying. In the end, the 5/2 cotton yarn will have about 2280 yards per pound.
The size gives us a very accurate size of the yarn, and if you need to get more, or something similar, you know exactly what size to look for, or you know how many yards you have in that one little ball and will know if you have enough to finish this project. Spinners use this method to know how to spin a yarn to match another one — it has to be of a specific thickness and twist to measure the same yards per pound as another yarn.
This only applies to cotton and linen. Wool uses a different yardage for the base number — worsted wool is usually measured at 560 yards per pound for a one-count yarn. That means that a skein of wool at that thickness of yarn will have 560 yards in it, and the count is the number of skeins that can be spun in that technique out of a pound of wool. A 20/2 is 20 skeins (or 11,200 yds) and this one is a 2-ply, so the total yardage in a pound is 5,600 yds. A yarn that is 12/2 would be much thicker having only 6,720 yds of singles, or 3,860 yds in a 2-ply.
To call a yarn “worsted” or “sport” means nothing since it still doesn’t tell me how many yards there are in this ball of yarn. It’s very inaccurate. Weavers and spinners have been using this system for hundreds of years… knitters are just slower to coming to a standard.
Learn to Spin Yarn – Drop Spindling Terminology
