Tutorial – Wraps Per Inch (WPI)

I’ve been working on a project using a package of “mill ends” that I picked up over a year ago. For those of you who aren’t familiar, mill end skeins are like remnants. There’s no weight, fiber content, or even brand listed on the package. I’m writing up the pattern for you, but there’s one problem –  I need to tell you in the pattern what weight yarn to use…and I have no idea what weight this yarn actually is!

No worries though, there’s a way to find out. First, I take my handy little ruler, and start wrapping the yarn around it carefully, starting at the 1 inch mark and going until I hit the 2 inch mark. See how all the strands of yarn are lined up next to each other and none are overlapping?

Wraps per inch method for determining yarn weight

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Now I just count how many strands there are in that 1 inch space, which here is 13. That’s the “wraps per inch” (wpi) for this yarn. For a more accurate measurement, I could have counted over several inches and averaged, or just wrapped several inches and counted a 1 inch space in the middle, but in most cases a rough estimate is all you really need.

So how does that translate to a yarn weight? There really isn’t one standard conversion table – there are a lot of different ones out there, and they’re not all consistent. Here’s one from Ravelry which would list this yarn as sport weight (size 2). However if you look at this guide from Craftsy, it would be considered a DK / Light Worsted weight (size 3). The Craft Yarn Council has overlapping numbers, so it could be either size, according to their guidelines. 

This is where a gauge swatch can come in handy. The problem with using a gauge swatch for sizing is that it is obviously dependent on which hook you are using and your own personal tension, so I only use it as a secondary point of reference when the wpi isn’t clear. In this case, I got 16 sts in 4 inches, using a fairly small hook (4 mm). Looking at the Craft Yarn Council Yarn Weight Standards chart, this seems to fit better with a size 3 yarn than a size 2. So for the pattern, I will recommend a size 3 yarn.

If you’re ever stuck with a mystery yarn and need to know what weight it is, now you know how to find out!


  • cdsnyder2014

    Thank you so much for the information. I have to admit, when I received your email, I was intrigued, and was pleasantly surprised when I read your blog. I love finding out new things that I never would have researched on my own. (And that’s the truth!!)

    Love your blog, keep up the great work!

  • Darlene P.

    Thank you so much for explaining so clearly this concept and giving links. I use mill ends all the time and generally I eyeball it, comparing it with other yarns. This is certainly more exact! This is a tip I’ll be using quite often from now on!

  • Jessica Serrano-Gregg

    Finally!!! I understand what WPI actually means and it’s very useful!!! I’m not sure why I just don’t visit your blog to find out anything and everything from the beginning! I should just print out your entire blog to reference. I do have a huge binder marked ” Pia Tutorials and patterns” that I reference a lot lol.
    I don’t always comment and I really should but I get so excited to try a new stitch from your well written crochet stitch tutorial repertoire… But Then I forget to come back and thank you! But thank you. I wish for you to really understand that it’s so much more than that for me and For some reason I understand your patterns, your tutorials and the way you explain things better than anyone else… We must talk the same way or something because I have trouble understanding most things lately… Brain doesn’t / isn’t what it used to be but I understand the way you write… The way you are able to convey the information And thank God because I really would have given up a lot of times out of sheer frustration, getting stuck on trying a new stitch that I couldn’t get right, or a pattern not written the way I could understand it but you have saved my sanity AND saved me from throwing in the proverbial “crocheted towel” lol and just giving up something I love to do but after I got sick things changed for me, not only physically but mentally as well. I don’t understand what I once could… It’s very emotional for me and reminds me that I’m not like I was before my illness so It’s VERY frustrating and and I get VERY emotional when I can’t understand things, it’s like opening up Pandora’s box. So I wanted to take the time to properly thank you and explain why it’s more than just a “hey, thanks for the tutorial” but why it means more to me. I appreciate the time you take to do these tutorials so I can learn a new stitch and especially explanations like this, WPI.. I heard the term before but never bothered to figure out what it really meant but I’m finding that it’s actually really helpful to understand the basic fundamentals of crochet and why the info is important. Your tutorials and explanations have helped me greatly because If I learn what it means and actually internalize and comprehend it as you explain it…then it’s so much easier to apply that info to an actual project. I didn’t realize WPI wasn’t just random, needless info but something that can help me identify the hundreds of unmarked rolled balls of yarn I inherited from gramma!!! And those Mill end grab bags too! Got some of those hanging around with some really unique yarn I want to use but didn’t know where to start with it. Anyways thanks, I get it now… I appreciate you and your time. You’ve helped me tremendously and I’ve never properly thanked you for that and if you knew me personally and my story, then you’d understand why it means so much because I literally thought I was going to have to give up something that I loved doing because I could no longer understand or process the information to do an actual project anymore so I kinda gave up for a while. Just reading a basic pattern had me in stitches… Lol and not the good, funny kind of stitches.. Haha. So from the bottom of my heart… Thank you… It seems so simple to say that and it really doesn’t do justice to what you’ve unknowingly given back to me. I wish there was a way to convey what it means to me other than by saying thank you…maybe I can send you some pretty yarn? Lol, unmarked, random unique yarn… But hey now I can find out the WPI and identify the weight for you!
    Yours sincerely, respectfully and with much gratefulness ~ Jessica

    • Pia Thadani

      Oh my goodness, what a marvelous comment! I’m kind of blown away and not quite sure how to respond (in a good way) 🙂 It means so much to me to hear that you find my posts useful and that you’re able to follow my patterns. Thank you for taking the time to tell me – it means more than you know 🙂

      • Jessica Serrano-Gregg

        Yeah, well I ran into the same problem trying to come up with a coherent and sincere way to thank you without sounding like a whiny baby ohhhh woahhhh is me kinda thing lol. I certainly am very empathetic and sympathetic to the fact that all of us have something on our plates… Most people have a story. I really really didn’t want to say oh hey I’m sick because I don’t want anyone to think I’m seeking pity or sympathy lol it’s just the only way I could convey to you that sometimes in life we go about our daily business such as you do, never ever knowing that you helped somebody or made a difference in their life somehow someway. You may think it’s only a crochet blog but to me…its more. It’s my therapy, it keeps my hands moving when they don’t want to work, or hurt or when they want to do their own thing like poke me in the eye lol.. Crochet Keeps my mind active and challenges my creativity, keeps my mind off the things I cannot change… Crocheting also keeps my mind from going to that deep, dark place that gets me all upset and depressed so you see why it’s kinda my outlet… My escape and my lifeline to keeping sane! So you see exactly why I wanted you to know that you may not think you’re doing anything special but… My dear, you really don’t know just how you may touch someone by simply sharing what you do! We don’t always know that the little things ( or what we might perceive as a little thing) we do can have such a huge impact on others. The truth is, they do.
        Just a funny story about why it’s important to me to keep learning and creating… My gramma passed away ( not the funny part) a bit ago and but she helped raise me and she started teaching me to crochet, well TRYING to anywho hehe, poor gramma lol… when I was about 6 or 7 years old but had a hellava time lol because I am lefty and she was right handed so there were a lot of fun and frustrating moments and memories I have of that special time spent with her. Poor gramma tried everything to teach me, mirrors, looking over her shoulder, facing her, upside down and inside out lol oh she even tried it left handed and I tried it right handed but I could never really get passed doing a lot of chains and single crochets so I think gramma finally gave up and taught me how to hand sew little Barbie clothes from discarded clothing. Now that I could do lol! But the memories are there for me and always will be something I cherish so very much so I became hellbent on learning so with the help of crochet geek and her left handed tutorials on you tube I finally was able to get it!!!
        But I digress, you have a family to care for and love and a household to run but you also have found the time to create an amazing community within your own web pages, blog; to share your talents, your creativity, you devote your time and share your knowledge out of a love for the craft and teaching others, carrying on a tradition… You do all this for FREE, never asking for anything in return. To me, that’s humbling and priceless but also you should know that you have made a difference to me personally and I’m learning that there’s only so much time we have… We have to make the most of the time we have and work with the cards we are all dealt in life. So for me personally, It’s important to let those people who’ve made a difference for me and my life, know what they’ve done. It’s important to let others know they are special and they are good and they are needed and appreciated. So thats the long and short of it and that’s why it was important for me to tell you thanks but REALLY tell you thanks and why thanks lol! So thanks!! Lol

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