Is fingering-weight yarn the same as sock yarn?

Nope. Well, not necessarily. 

Let’s back it up a step, though. 

“Fingering-weight.” Where does that term even come from? The most-often cited etymology is from the French phrase “fin graine,” meaning “fine-grained.” As a French speaker… well… that gets some serious side-eye from me. The word order is wrong, and it doesn’t appear that “graine” is a word that has applied to wool or yarn*. Additionally, as Norman at the Nimble Needles blog points out, yarns in Europe are sold by the size of needle you would use with them and not by general category. Norman did some excellent detective work and tracked down what he believes to be the origin of the term - in the Scottish National Dictionary, a type of woolen cloth is labeled “fingering,” which the dictionary proposes comes from a spinning technique that, by that time, had been lost in terms of its relationship to the creation of the yarn used in the fabric. 


(Seriously. Go read Norman’s post. It’s FASCINATING.)


Fingering-weight yarn, according to the Craft Yarn Council standards, averages a single crochet gauge of 21-32 stitches in 10 cm / 4” and a stockinette gauge of 27-32 stitches in 10 cm / 4”. That’s an incredibly wide range (especially for crochet). The “put-up” - how many yards there are in a standard skein or hank - can range from 366 meters / 400 yards in 100 grams to 425 meters / 465 yards in 100 grams. That’s a 14% difference in yarn thickness between the ends of the range! 

Why, for so many people, does “fingering-weight” then automatically equal “sock yarn”? Smaller stitches tend to both feel better on the foot and wear better over time in high-friction contexts - so it makes sense to make socks out of finer yarn. And why is THAT, you might ask? The soles of our feet are incredibly sensitive. Think of how fine some of the grit is that you find in your shoe after a walk on the beach, and how disproportionately annoying it is to figure out what’s bugging you in your shoe before you sit down and tap it on a bench or a curb.. The purl bumps on the inside of a sock are more uneven than the knit side, so if you have larger yarn in a sock, everything about those purl bumps is going to feel unusually irritating. (There is a solution to this - called a “princess sole” - which has you purl the stitches on the sole of the sock so that the smooth knit-stitch side is directly against your foot.) Using large yarn means your stitches are larger, and more of each stitch is going to be exposed to abrasion and wear away more quickly than the small stitches. 


So if fingering-weight yarn isn’t automatically sock yarn, then what gives? What IS sock yarn? That’s an excellent question and one that will kind of depend on who you ask. At the shop, I maintain that sock yarn has two very important characteristics - 1, it’s tightly plied. 2, it contains some sort of fiber that is going to help combat destructive abrasion. Tightly plied yarn is going to expose less of each strand of the yarn (called a single when we’re talking about yarn construction), and it’s going to be springy - and therefore able to stretch and give in response to the movement of your foot. The second fiber is going to strengthen the yarn - it’s often nylon, but sometimes silk or mohair are used instead. There are several yarns on the market in DK-weight and worsted-weight that are specifically pitched as sock yarns because they meet these two criteria, and I agree with that classification.

The takeaway - there are several different positions on this, but I’m going to come down on the side of saying that it’s only sock yarn if it meets specific conditions that will help it resist abrasion and stretch to help with the negative ease that most socks require. Fingering weight can be all over the place in terms of fiber content and yarn construction, but if it doesn’t have a strengthening agent or tight spin, I’m not going to recommend it for durable socks - and therefore it’s not a true sock yarn. 

*I need to absolutely confirm this with my big French dictionary, but it is currently behind about 35 kg / 80 lbs of boxes in our home library - the online version of this same dictionary has definitions from the 17th century, which do not include fabric / fiber grain among its definitions, either.