Knitting Blog

Mystery Stash Yarns: Determining Yarn Weights

It’s difficult to organize your yarn, especially if most of it has been given to you by family members cleaning out their attics. Or maybe your stash is composed of skeins you picked up from secondhand stores along with scrap yarn from old knitting or crochet projects.

Inheriting yarn and having a huge stash to choose from is great, especially for scrap yarn projects. But when you’re using these mystery bits and pieces for projects, you need to know the yarn weight in order to substitute the correct yarn, and often this information isn’t available on the yarn. It could be because the label is torn or yellowed — or maybe there’s no label at all.

Don’t worry. All is not lost! You can calculate the yarn weight with a handy little knitting secret called WPI (wraps per inch).

Calculate wraps per inch - seam gauge and yarn around pencil

How does WPI work?

Yarn weight is determined by the diameter of a yarn strand? Bulky-weight yarns work up quickly because the yarn strand is thick in diameter. Lace weights are airy because their strands are thinner.

Wrapping the yarn around the pencil determines whether the yarn wraps many times around the pencil, like a lighter-weight yarn would, or the yarn doesn’t wrap as many times around the pencil, like a heavier-weight yarn would.

See the difference between the two yarn weights here? The first is a DK weight and the second is a super-bulky yarn.

Lace weight yarn wrapped around needle Super bulky yarn wraps per inch measurement

What you’ll need

  • Your mystery yarn
  • A ruler
  • An object with a consistent circumference, such as a pencil

It’s also an option to wrap your mystery yarn around a ruler, eliminating the need for an object with a consistent circumference. You can even buy a special WPI (wraps per inch) tool that has notches to hold the yarn in place while you wrap and comes with a handy card to help you categorize.

You can wrap the yarn around your knitting needle or crochet hook — but only if the tools has a consistent circumference. If it tapers or has an ergonomic handle, it won’t work.

How to determine your yarn weight

Begin by wrapping the yarn around the pencil. Don’t wrap too tightly. The goal is to get the yarn strands as close as possible without overlapping them or leaving holes.

Measuring wraps per inch with a needle gauge ruler

Usually wrapping about an inch should give you an accurate measurement, but if you’re using a yarn with a shape that isn’t consistent, like an eyelash yarn, you should wrap it for more than an inch to get the most accurate measurement possible.

Once you’ve wrapped your yarn, count the number of times you wrapped it around the pencil within the first inch. Then, compare that number with the numbers on the WPI chart below.


WPI chart

Yarn Weight Wraps Per Inch Gauge
0 – Lace weight yarn >35 >8.5 sts/inch
1 – Fingering weight yarn 19-22 7-8 sts/inch
2 – Sport weight yarn 15-18 5.75-6.5 sts/inch
3 – DK weight yarn 12-14 5.5-6 sts/inch
4 – Worsted weight yarn 9-11 4-5 sts/inch
5 – Bulky weight yarn 7-8 3-3.75 sts/inch
6 – Super-bulky weight yarn <6 1.5-3 sts/inch

So for example, if your yarn wrapped around the pencil eight times in one inch, your yarn is bulky-weight. If the yarn wrapped around the pencil 16 times in an inch, it’s a sport weight yarn.

If you were wrapping a yarn with a funky texture as mentioned above and you wrapped extra inches, just do a little bit of math to find your WPI. If your eyelash yarn wrapped around the pencil 30 times in 2 inches, for instance, just divide 30 by 2 to find that your WPI is 15, making your eyelash yarn sport weight.

Still can’t figure it out with wraps per inch? Here are two other methods you can try to determine that yarn weight.

Master Wraps Per Inch & More Yarn Essentials

types of yarn guide

Learn everything you need to know about yarn weights and fiber types to make savvy selections and achieve superb stitches.Get My FREE Guide »

Do you have a lot of mystery yarns in your stash? Have you ever used this handy WPI technique to calculate the yarn weight?

Editor’s Note: This post was originally published in November 2013 and was updated in February 2018.



Very helpful method for all of those mystery skeins in my stash–thanks for sharing, Ashley!


A good guide but I am confused on one point: I don’t understand how you can substitute the ruler for the pencil, as the yarn required for just one wrap is different for both, correct? Doesn’t the thickness of the pencil orruler or other object matter in the calculations?


Hi Eva! The circumference of whatever you’re wrapping the yarn around doesn’t matter because what we’re determining here is the diameter of the yarn strand. Wrap the same yarn around a ruler, a pencil, a dowel — anything with a circumference that’s consistent — and you’ll get the same wpi results for all of them. It’s the horizontal measurement that matters, not the vertical measurement. Hope that helps!


Oh, of course! (smacks forehead) That makes perfect sense now. Thanks so much for the explanation.


For years, I always thought you needed a special WPI gauge to measure. Until this post. Total smack on the forehead moment here, too.? Thanks, Ashley! Now I’m definitely going to check the WPI on my handspun.


Hahaha I thought exactly the same as Eva, then read Ashley’s answer and went “Doh” *tap on the forehead*!
Thank you so much for this article, very handy

Lana Siebert

I don’t think so….it is the width of the yarn that is measured…not the length. So the object that it’s being wrapped around has no bearing. Only the amount of times it has gone around. Then count. If you wrap around a pen, ruler or a spray bottle, it will make no difference in the amount of times it goes around for the length of an inch.

Debbie Winn

Great information! I’ve only been up for about an hour this morning and already I have learned something new. Thank you for sharing this. 🙂


love this! question…. will doing more than an inch of wrapping still work for a thick and thin (irregular diameter) type yarn?


Hey Kelly, the more you wrap an irregular diameter, the better your number. It makes it a little harder, of course, but wrapping it for several inches and taking the average is the safest bet.

Tamara Morgan

This is really handy, thanks!

However, I think it would be somewhat less confusing to not use the word “weight”. You aren’t calculating the weight, but the category of the yarn (Lace, Fingering, DK, etc). I know that these are known as ‘weights’, but when I think of weight I think of yardage per 50gm ball, for example, not the stitch count.

Which, yes, all amounts to the same thing in the end, but I thought initially you were going to teach how to actually weigh our yarn (which can also be done to determine potential gauge of a mystery yarn).


Thank you. Very useful information.

Judith Hudson

Thank you for an interesting article. How can I tell if an unlabeled yarn is acrylic or wool?


I realize this question is a few years old, but for other readers seeking the answer, you can figure out what kind of fiber you are working with by using a burn test. This works for fabric also. Google “fiber burn test,” and you will get plenty of helpful articles on the subject.


New response to old question – this won’t for everyone but…
I hold the yarn to the inside of my arm. Wool starts to prickle after a few seconds. Acrylic feels harsher than alpaca. Cashmere feels like heaven! Silk and bamboo blends feels “different”. I know – very scientific.


Judith: burn the end of the yarn. if it turns into a hard plastic ball, it is acrylic; if it turns to ash, it is a natural fiber: wool, cotton, etc.


Hi, that is a great help! But does it also work with centimeters instead of inches?


Sure! You’d just need to convert the WPI chart to centimeters. The point is to make sure you wrap a large amount of yarn to get the most accurate reading.

Peg Cates

Is there a way to tell if the yarn is wool or other fibers?

Hannah Long

Thanks for the info! If the wpi is between 22 and 35, is it fingering or lace? Thanks for this handy trick!


Thank you this is really useful information but are these weights American because I think they differ from UK weights. For example I don’t know what is meant by worsted, fingering or sport.


I have the wpi tool, but it is always useful to know more than one method of doing anything. Thank you for posting this.


I’m sorry but as far as I can tell, this method is not a reliable way to determine the weight/gauge of a yarn. It’s been show in other publications (Spin Off magazine I believe) that given the same instructions, different people wrap the yarn at slightly different tensions, causing a wide variance in measurements. Most yarns are stretchy. When you say ‘Don’t wrap too tightly’, exactly how tight is that? For example, small changes in tension can cause the measurement go from 13 (DK) to 15 (Sport) WPI. Which one is it? A popular knitting magazine used to list WPI for yarns recommended in their patterns. One day I sat down and compared WPI for one specific yarn across a year’s worth of issues of the same magazine. Each issue had listed a different WPI for the same yarn! Some issues listed a WPI indicating DK, others indicated Sport. This is a neat method for getting a very rough approximation, but IMHO I’m not sure how useful it is.

Onda G

In the end it comes down to gauge. Taking the time to make a swatch is the tried and true method of knowing if a pattern will work with the yarn in stock. Our individual tensions as we crochet is just as much a variable as the tension we’d use to wrap the yarn around the ruler or pencil. It gives a rough idea, then swatch. Thanks for sharing this technique. It was explained very clearly.

Gwendoline Davina

I would like to add my thanks… Three weeks ago I discovered ‘pin weaving’, I love to weave but do not have the time or space to set up a loom so these little looms are perfect. I have not knitted for about twenty years and even then did not know any technical terms so when I read “wraps per inch” in my instructions I was completely flummoxed. Your simple explanation plus all of the above postings have really helped me to understand.
Thank you so very much xx.

Sylvia R

So glad this post is still online! You gave me instantly exactly what I was looking for. I need to (hand)spin some “worsted weight” yarn for a communal afghan (which will be individuals’ knitted squares pieced together), and I really needed a better idea of how thick such yarn would be. Thanks!

Jean Murri

Thanks soooo much!!!

Janet Downs

Such a useful way to identify yarn weight but I’m not sure of the British equivalents -Worsted, Fingering etc? Can you help?
Many thanks

asherah arts

For all the people looking for British equivalents, this has some other excellent information

Ply refers to the strands which are spun within the yarn, so a ply can be a bit of a generalization when it comes to thickness so the equivalents are a general layover and there may still be outliers.


Thank you! Very helpful.

barbara wood

Do you have a conversion chart to English wool weights please ?

Sharon w.

A useful bit of information would be how to tell if a hank or skein of fluff is either wool, or acrylic or even superwash

Ruth Greenawalt

thanks for this great info, I have many unmarked skeins.

mrs kishwer malik

I am new and want to learn every crochet stich step by step. Hope you will help me . thanks

Harlene LeVine

Is there an easy way to determine the yardage of a yarn in my stash? I can figure out the gauge, needle size, comparable yarns, but I never know how much a ball of yarn contains. I’d love any input.


I’m sure this is far too late to be of any help, but yes, there is a way, assuming that the yarn has a fairly consistent twist and thickness.

Measure the weight of the whole ball. Then measure out a set amount of your yarn – 10 yards is a good amount – and weigh it. Divide the first number by the second number then multiply by 10 (or whatever amount you measured for the second number), and you have your approximate yardage.

Of course, I’m assuming this is a handspun, as generally speaking commercial yarns do say on their ball band what their yardage is.

Harlene LeVine

Took me a long time to finally get back to this for the answer. Your idea is perfect. Thanks.


Many thanks for this useful tip about determining yarn weight. I recently bought some wool on a trip to Norway and was not sure whether it was 4ply or dk as there was no indication on the label. Turned out to be dk.


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thyis blog, I hqve read all that, soo now mе alѕo cߋmmenting at this plaϲe.

Carolyn Chiverton

I really like your writing style, good information, appreciate it for putting up : D.


I have a question maybe you can help…. I’m working on a pattern and it calls for this yarn: Simply Soft (170 g/6. oz;288 m/315 yds), Sizes S M L/XL 2XL 3XL
Main Color (MC)
Victorian Rose
4 5 6 7 8
One size US I-9 (5.5 mm) crochet hook, or size needed to obtain gauge.
Stitch markers or scraps of yarn. Yarn Needle
In Fsc, 12 sts = 4″/10 cm; In body pattern stitch, 2 (shell, ch 2) pattern repeats = 3″/7.5 cm and 5 rows = 4″/10
cm…. My question is what yarn could I use instead of the simply soft???


You’ll need to play with the guage. If you can get to a store selling the yarn recommended, eyeball it, then read the labels of comparable yarns to find a match. It will be close. Or search for substitutions on-line. I’m someone who substitutes all the time, I also am not a perfectionist! So I have more leeway than somebody who needs it to turn out exactly

Marion Darlington

Just what I needed for my handspun! Thank you so much.


Hi: I’m making a warp for some scarves out of multiple size and textured yarns. I made a sample wrapping and had an average of about 9 wpi: so is my sett 9 epi? I had 89 threads in my 9 in. Wide wrap. I’m confused. Your help will be much appreciated.


Thanks for this helpful article. As a very new knitter (I began in November 2016), I wondered how I might keep track of my yarn – which company made it? How thick is it? What’s the manufacturer’s ‘name’ for the colour? What needles/hooks are recommended, etc.?

Right from the get-go, I decided I would tape a few pieces of the yarn to its paper packaging (this is especially helpful for variegated yarns, as it lets you see the variations in colour). These packages, with the yarn scraps taped to them, then can go into labeled manila envelopes.


Jeff, I use a hole punch to make two holes in the label that came with the yarn and then attach a length of the yarn through the holes and tie the ends together.


Jeff, join Ravelry, and use its tools to keep track of what yarn you own (‘stash’) and all its details. It’s a free site and VERY useful. Best part is that your notes to yourself can’t get lost among the clutter of yarn and patterns.


Im from Europe and we use centimeter here. Now I would like to buy some similar yarn at an UK online shop. So according to 5cm is about 2 inches. Can I wrap the yarn for a length of about 5cm on a pencil and divide the result through 2 to get the official WPI? Does that work? Thanks so much, Nina.


Nina, that’s exactly right.


Thanks for the breakdown, however, I noticed an error. You wrote:

0 – Lace Weight Yarn
WIP: > 35

I think that should read WPI: < 35

I just tested my yarn and got 28 WPI, if your chart is correct, my yarn weight is unidentifiable, ad it is "less than" 35 and does not conform to Fingering WPI: 19-22.

Kristin Doherty

Thanks for letting us know!

MicheLe Ann Richter

This is great … but how do I find out the weight (size) of the yarn, without being in possession of it? For example, a few websites that sell yarn on closeout websites, have the grams/ounces and the length in meters/yards… but not the size/weight of the yarn. They do put a hook/needle up in the picture, that says 3.0 mm or 4.0 mm, but I know not everyone uses the appropriate size needle/hook for the yarn they are using. How do I know if they are using the standard that most manufacturers use? I tried asking them, but no one has responded yet and it’s been 3 days and I was hoping to buy product before the sale ended.


Thank you so much for this common sense explanation. I have often been puzzled by the size of my yarn bundles and this is great


This is an amazing piece of information. Thank you so much.


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