My New Decision on WPI and Yarn Weights

CST WPI Chart (web).jpg

It’s a dilemma.

Yarn Weight vs WPI


Any time you start to research, discuss or calculate using yarn weight, it’s easy to get confused.  This is due in great part to the guidelines being so different from site to site, group to group and person to person.  There is no “standard” no matter what people tell you.  The closest we’ve come is the Craft Yarn Council’s guideline for yarn weight.

Same goes for WPI (wraps per inch)

When I was trying to decide which set of guidelines to use for descriptions for the site, it got to be almost depressing.  I trust the folks who tell me 19 – 22 wpi is Fingering.  I trust the folks who tell me 14 wpi is Fingering.  Those are vastly different numbers and would result in extremely different swatches. To complicate things further, I had already tagged much of my yarn by simply using the manufacturer's descriptive wording.  They called it a Fingering, so I did etc. 

I've changed my mind, and decided to establish a "standard" if you will, for what I will classify my yarns to be.  This means some of my tags won't have my new classification on them.  I will make note of that on the Shop pages, and I hope this does not cause a problem for customers.  I just felt it was disingenuous of me to call the same WPI by different classifications simply because various yarn manufacturers had no standard to go by.

When I first heard about WPI, I was a lot younger, and deeply immersed in weaving.  WPI was a very important tool for me as a weaver, and it told me a great deal about how much yarn I needed to purchase to have a sufficient amount for warp and weft. 

My personal opinion:  WPI is a better tool for the weaver than it is for the knitter, and I’ll tell you why.  Warp yarns are pretty much under the same general tension when the loom is dressed.  Weft yarns are typically under similar tension, not only within each project, but generally from one project to another, though the weight, ply, and spin of  the yarn here does create some variances.  But for the most part, WPI could be counted on as a good general guideline for yarn needs.  It also allows the weaver to take an educated guess as to what the final fabric will look and feel like once tension is taken off the loom ( though this really depends on the structure of the yarn and the content a great deal ).

For folks who knit and crochet, WPI is a lot more loosey/goosey.  For starters, it depends on the size of needle or hook the artist chooses to use. Things are complicated even further with variables such as how tight of a knitter are you?  What type of stitch are you using?  What is the type of stitch pattern called for?  These are just some of the added variables that someone who knits/crochets has to consider, over what we had to deal with as weavers.

Basically, it all comes down to the “dreaded” gauge swatch.  Take any WPI or Weight of Yarn Indicator as a guideline only.  One person’s DK could easily be another person’s Sport.  This means that the yarn the designer used, that was labeled as Sport weight might be more like the Fingering or perhaps even the DK that you have as stash yarn.

In my opinion, the only really true hard and fast rule is:  There is no hard and fast rule.

For what it’s worth, the above is the resulting chart of typical WPI / Yarn Weight I ended up with, based on averages of what I found in commercial yarn, what the Craft Yarn Council states ( based in part on Ravelry ), what Craftsy and Knitpicks state as well as some yarn manufacturers.


PJ Holtzman