Wraps Per Inch is a Mystery to Me

This afternoon I set out to measure the weight of some yarn I had just spun. Eyeballing it, I expected it to come out as a fingering weight yarn. So I pulled out a ruler and commenced a-wrapping. It came out to 18 wraps-per-inch (WPI).

Next, I called upon the mighty internet to find a WPI conversion chart. I said to myself, “This whole spinning and knitting thing has been around  for so many centuries. There must be a standardized conversion chart.”

Silly me.

The results of my search were so wildly and comically inconsistent I had to write them down.

Wraps Per Inch, as measured by many inconsistent internet sources.

And having written them down, I felt compelled to share the pain with all of you.

Not only do different sources fail to agree, they seem to be actively at war with one another.

Depending on the source you consult, my hand-spun yarn could be considered sport weight (Knitpicks, Spinderella) or lace weight (Woolfestival, Yarnwench, Woolery, Crochetspot).  Yikes.

The grossest irregularities come when measuring WPI for lace weight. The WPI values range from 18 to 40. Seriously?

I was floored to find out that the Craft Yarn Council has nothing at all to say about WPI in their standards. Neither does Spin-Off magazine (although there appears to have been an article called Debunking the Wraps-Per-Inch Myth in the Fall 2010 issue…I need to get my hands on that.)

So, a question for all you spinners out there: how do you evaluate the weight of the yarn you spin? If WPI is such a laughably useless  measure, what do you use instead?

I need something I can depend on. I guess there’s nothing for it but to create my own custom WPI charts. What a pain.

I’m a new spinner so perhaps I’ve missed something. Save me from making my own WPI charts. What do you know that I don’t?


  1. Yeah, that’s a problem. I read the “Debunking the WPI” article and in fact, probably have the magazine laying around somewhere here. It basically said “WPI is bunk” but offered no viable alternatives.

    Also, depending on how tightly you wind the yarn around the ruler / tool, you can affect the WPI measurement itself, because after all, you’re measuring the width of something soft and squishy and if you stretch it too much, it gets thinner.

    I have two methods that I use, depending on the level of accuracy I need:
    1) Root around in the stash to find something in commercial yarn that is relatively the same size and see what the manufacturer says, or
    2) Swatch and see how many stitches per inch I get.

    After a while, you will develop an eye for it and you can tell the difference from looking at the yarn. In the meantime, that gives you a couple of options depending on your need at the time. Option 2 is a pain but it’s what I use if the finished yarn is going to be used in a garment that has to fit. In that case, it’s pretty much killing two birds with the same stone since I would have had to swatch anyway and I always wash/block my swatch. (I learned that particular lesson the hard way when a sweater doubled in both length and width when I got it wet to block it. That was expensive commercial yarn so now I am uber-careful and block all swatches before counting.

    Hope this helps.

  2. All I know about wraps per inch is that I have a tardis key chain that can calculate it.
    Obviously calculating it doesn’t really mean much, but it’s a tardis!

  3. What Mardee said. I know that a 100-gram ball of commercial fingering-weight sock yarn has around 430 yards, that the same amount of commercial worsted weight yarn has around 200 yards, etc., so I use a combination of yardage/weight and eyeballing the yarn and comparing it to commercial yarn. But the only way to know for sure is to swatch.

  4. I hate swatching but it really is the only way to get an accurate idea of the weight your hand-spun is. I’ve gone with the eye-balling method to decide, and most of the time it works out… especially since you are probably going to swatch before you knit anyway, right? *hahaha* yeah, sure I am 😉

  5. Been there, done that! I find WPI useless and generally ignore it. I tend to hold it up against commercially produced yarn and sort of guess, or sometimes I’ll knit up a swatch and see what the gauge is typical for.

  6. My thought would be to use a niddy noddy to get the total yardage of your yarn, and then use a scale to weigh it. Then I’d compare that to similarly sized commercial yarns by using the YarnPro phone app, which would verify whether or not your spun yarn is similar to your standard yarn.

  7. I agree that swatching is the only way to know for sure. But it seems a poor choice when all you want to do is evaluate the qualities of what you have created in a general way. For a specific project, sure, I’ll swatch. But if I’m not sure it sounds all that efficient for general purposes when all I want to find out is “should I put this in the worsted bin or the dk bin” not “is this suitable for this specific sweater.” Maybe this will sound silly, but I quail at the thought of “wasting” a length of my handspun in swatching and washing it just to find out its relative weight. When I only have 200 yards of something, sacrificing even a small portion is hard to do.

    The proportion of yardage to weight, in comparison to other similar yarns, seems to be be the next logical step, from what everyone is saying. I think the time has come for me to start keeping a detailed spinning journal. I’ve been resisting for reasons that have nothing to do with principle and everything to do with laziness. The end is nigh.

  8. Throwing my hat into the ring for a yardage to weight comparison. It seems to work pretty consistently so I at least have an idea of where I’m coming in at with hand spun!

  9. I am spinning for 3 years now and just eyeball my yarn. Then I try knitting a swatch on different needles to figure out what # I need. That’s all. I did read the article too and it is true – not easy to measure WPI consistently. He gives some ideas to to even it out. But… for the same yarn yours and mine would slightly different. I think it is a silly measurement in spinning, or I would say – not quite reliable, just an approximation.

  10. I usually use the iSpinToolkit app on my phone for eyeballing purposes, and combine that with the yards per weight chart from Spinderellas… but I figure it’s all best-guess until it’s time to swatch.

    • I’ll have to check out that app. I agree that all of these tools are only best-approximation and that searching is the true test. But we all need tools to help us ball-park out initial estimates. I’m still kind of amazed how much variability there is in what seems like a very straightforward measurement method.

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