Beginner’s Guide to the Standard Yarn Weight System

by | Jan 18, 2020

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Need to choose yarn for a project?  How do you know if your yarn is the right thickness?  Use the Standard Yarn Weight System to find out!

If you’ve ever been yarn shopping, you know that there are loads of different types of yarn out there.  There are so many different colors, textures, and fibers that if you don’t know what to look for, it may be a bit overwhelming to choose just one yarn for your project.

But there’s another thing to consider before you decide which yarn to use: thickness.

The thickness of a yarn can have a huge effect on how your project turns out.  If you’re following a pattern, using yarn that is the correct thickness is very important.

Too thick, and your stitches will be too large, making the project come out bigger than you wanted.  If it’s too thin, your stitches will be too small, and your project won’t be big enough.  Getting a yarn that is the wrong thickness can throw off your gauge and ruin your project.  (See this post for more info on Knitting & Crochet Gauge.)

So, how do you compare the thickness of a yarn?  How do you know if the yarn you want to use is the right size for your project?


This is where the Standard Yarn Weight System comes in.

Yarn weight does not refer to how much the skein of yarn weighs in ounces or grams.  The “weight” of a yarn actually refers to the thickness of the yarn.  The Craft Yarn Council has designated 8 different yarn weight categories.  These categories help us know how thick a yarn is, and whether it will be suitable for use with the pattern we want to follow.

We can know what weight category a yarn falls into by checking the yarn label.  Yarn labels are required to list the weight category of the yarn, as well as the fiber content and the amount of yarn in the skein.

Some manufacturers use the symbols provided by the Craft Yarn Council, which show a little picture of a skein of yarn with a number on it.  The number and the category name below the symbol tell us what weight the yarn is.

However, some manufacturers only give the name of the yarn weight without the category number.  That might not seem like a big deal, but sometimes, the weight categories are called by different names.  This is why it’s important to know the other names used to denote yarn weight, so you’ll know which category a yarn falls into, even if the number symbol is not given.

The photo below shows examples of 7 out of the 8 weight categories.  Notice how the yarn gradually gets thicker as the category number goes up.

photo comparing the different thicknesses of yarn in the standard yarn weight system

Source of Yarn Weight Symbols: Craft Yarn Council’s


#0 Lace

The #0 category is for the thinnest of yarns.  Lace weight yarns are made for making knitted or crocheted lace, which is often done on larger needles or hooks for an open, lacy look.  Size 10 crochet thread also falls into the Lace weight category.

#1 Superfine

This category is one of my favorites!  #1 Superfine yarns include sock yarns and fingering yarns, and make a lightweight fabric.  These yarns are great for socks, shawls, scarves, clothing, and just about any project where you want a light, drape-y fabric.

Use #1 Superfine yarn for these free patterns:

#2 Fine

The #2 yarns are often labeled as Sport Weight.  These yarns are a bit thicker than Superfine / Fingering yarns, but still create a lightweight fabric.  Many baby yarns are sport weight.

Use #2 Fine yarn for these free patterns:

#3 Light

The yarns in the #3 category also tend to be rather lightweight.  These yarns may be labeled as DK weight or Light Worsted, but both terms refer to yarns of the same thickness.

Use #3 Light yarn for these free patterns:

#4 Medium

Now we’re starting to get into the medium weight and heavier weight yarns.  #4 yarns are very common in stores, and I think they are probably the most popular.  Worsted weight and Aran yarns fall into the #4 Medium category, but some Aran yarns tend to be slightly thicker than Worsted.

Use #4 Medium yarn for these free patterns:

#5 Bulky

Bulky yarns are great for when you want to make a thick, squishy project in a short time.  #5 yarns may also be labeled as Chunky, Craft, or Rug yarns.

Use #5 Bulky yarn for these free patterns:

#6 Super Bulky

These yarns make any project work up quickly.  They are very thick, so you’ll need some pretty large hooks or needles to work with them!

Use #6 Super Bulky yarn for these free patterns:

#7 Jumbo

The Jumbo category is relatively new.  These yarns are so thick, you knit or crochet them using your hands and arms instead of hooks and needles!  I have not tried working with Jumbo yarn yet, but if I do, I’ll be sure to post a photo. 🙂

The Craft Yarn Council has a page on their site with a chart (here), showing the recommended hook and needle sizes to use with each yarn weight, as well as the recommended gauge.

New: Here’s a free knitting pattern includes instructions for 6 different yarn weights!

Easiest Knitted Hat – Free Knitting Pattern for Beginners


The Length to Skein Size Ratio

Although the weight categories give a guidelines for yarn thickness, there is still some variation in thickness, even among the same category.  For example, two yarns may both be labeled as #4 Medium, but one may be slightly thicker than the other.

In most cases, as long as the yarn you want to use is in the same category as the yarn used in the pattern, it should be okay to substitute.  However, if you want to be even more precise with your yarn substitution, you can look at the ratio of yarn length to skein size.

Comparing the Length to Skein Size Ratio Between Yarns

For example, let’s say I’m following a pattern that calls for #3 DK weight yarn.  If the yarn my pattern calls for has 127 yards in a 50 gram skein, and the yarn I want to use has 123 yards in a 50 gram skein, those two yarns will be very similar in thickness.  However, if the yarn I want to use only has 105 yards in a 50 gram skein, even if it is still #3 DK weight, that yarn will be slightly thicker than the yarn called for in the pattern.

If the yarns you are looking at do not come in the same size skeins, say, if one comes in 50 gram skeins and the other comes in 100 gram skeins, you can just divide the numbers on the 100 gram skein in half to know how much yardage would be in 50 grams.  Or, if you prefer ounces, you can divide the number of yards in the skein by the number of ounces to find the number of yards per ounce for each skein.

Again, it is generally fine to just pick a yarn that falls into the same weight category as the yarn called for in your pattern.  The length to skein size ratio is just a way of making an even more precise yarn choice.

Standard Yarn Weights in Other Countries

The Standard Yarn Weight System is mainly used in North America.  However, the UK, Europe, and Australia use a different classification method for labeling yarn by its thickness.  If you’re yarn shopping in another country, you’ll want to check into the yarn weight system that is used there.  Here’s a conversion chart comparing Standard Yarn Weight to the other terms used around the world.

So when you want to follow a pattern, and you go to buy yarn for the project, make sure the yarn you’re getting is in the same weight category as the yarn used in the pattern.  Along with checking your gauge, this will help make sure your project comes out the right size!

What do you think of the standard yarn weight system?



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Need to choose yarn for a project? How do you know if your yarn is the right thickness? Use the Standard Yarn Weight System to find out! #crochetyarn #knittingyarn #knittingproject #crochetproject #crochettips #knittingtips
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  1. Jen

    I find it hard to estimate how many skeins of yarn I will need if the pattern and/or the skein doesn’t list a length. How can I estimate the length of yarn from the bulk and the weight?

    • Yay for Yarn

      Hi Jen! If your yarn label does not specify how many yards (or meters) of yarn are in the skein, here are a couple of articles explaining how to estimate the yardage of a particular yarn based on the thickness and the weight:

      If the pattern doesn’t give a length for the amount of yarn needed, I personally would not suggest following that pattern unless it gives a number of skeins of a particular yarn AND you can find the exact yardage per skein info for that yarn. If your pattern tells you how much yarn is needed in skeins of a specific yarn (like “KnitPicks Brava Worsted, 6 skeins”), and you can find the info for how many yards are in a skein of KnitPicks Brava Worsted, then you could use that to find out how much yardage that would be equivalent to in another brand of yarn.

      If I were wanting to follow a pattern, and it said something like, “500g of worsted weight cotton” and did not give yardage or any other info, I would most likely look for a different pattern. The amount of yards of yarn in 500g of one brand of worsted weight cotton can vary quite a bit from 500g of another brand of worsted weight cotton. If some of those important and necessary details are left out of the supplies list, that would indicate to me that the pattern has not been edited or checked for errors by a technical editor, and there may be errors or vaguely written instructions in the rest of the pattern.

      I hope this helps!

  2. Linda wirz

    Hi. What is the mathematical formula for using a different yarn than the one that the pattern calls for, so that the size is the same?

    • Yay for Yarn

      Hi Linda. There is not a universal mathematical formula for changing a pattern to a different yarn weight. Every knitting or crochet pattern is made of a whole bunch of mathematical formulas that determine the number of stitches, rows, increases / decreases etc to reach the finished dimensions based on the size of the stitches. The formulas used will depend on how the item is constructed, the height to width ratio of the stitches, increase / decrease rates… basically a pattern is a series of formulas written out as row by row instructions. For example, on my last crochet cardigan pattern, it took about 100 lines of spreadsheet formulas with a separate column for each size to determine all of the numbers needed for the pattern instructions. (This does not include the written instructions on where to work the stitches or anything, just the stitch counts, row counts, finished dimensions, ease, amount of stretch, amount of yarn required, etc.) So unfortunately, there is no such thing as a single formula that will help you change a pattern to a different yarn weight. You would have to recalculate all of the formulas that the pattern is made from with the new numbers you get from your gauge swatch in the new yarn. I do not recommend attempting that unless you are already comfortable designing patterns and working with the formulas needed to design a pattern from scratch. I hope this helps!

  3. LyndA

    I have several older sweater patterns that use the old worsted weight yarn. None of the new yarns look right as the 4 is skimpy and limp. Are there any other countries or small American companies who make the old style worsted weight yarn? Any creative small artisan yarn makers?s Thanks

    • Yay for Yarn

      Hi Lynda. I am not familiar with what the older yarns were like, so I wouldn’t know the answer to your question. The oldest yarns I have worked with were circa 2005. I do know that there are sites dedicated to vintage yarns and patterns, so maybe one of those might be able to help you. Sorry I couldn’t be of more help!

  4. Dana

    This system (wraps per inch ) always has confused me.
    There would be a huge difference using a pencil versus a 2 inch wide ruler to wrap the yarn around.

    Please be kind enough to explain this to me.

    Thank you, Dana

    • Yay for Yarn

      Hi Dana. If your wraps per inch test is not consistent, here’s something to keep in mind. When you wrap the yarn tightly, or put a bit of tension on it as you wrap, that stretches the yarn a bit and causes it to measure thinner than it actually is. I would suggest using a ruler, laying the yarn out on the table, and rolling the ruler to wrap the yarn instead of wrapping it with your hand. This keeps the yarn wrapped around the ruler with as little tension as possible, so you can get an accurate measurement. I hope this helps!

  5. Theda

    What is DK yarn?

    • Yay for Yarn

      Hi Theda! DK stands for Double Knit, and it is a term for describing yarn thickness. As mentioned in the article above, DK yarns are in the #3 Light category, which is also called Light Worsted. I hope this helps!

    • Becki Jameson

      Could you also tell us how two yarns can be held together while knitting, would that make it in effect equal to a heavier weight of yarn? For instance if two of #1 weight is equal to #3 weight and so on.

      • Yay for Yarn

        Hi Becki. When you hold two yarns together, it is much thicker. However, I do not know all of the precise weights of all of the combinations. I do know that two strands of #4 worsted weight yarn are similar in thickness to a #5 bulky yarn. I would recommend holding the two yarns together and using the wraps per inch test to figure out what yarn weight it is now equivalent to. To do this, you would take the doubled yarn and wrap it around a ruler, pencil, or knitting needle. You want to wrap it around without pulling it tight (tutorial here). When you count the wraps per inch for the doubled yarn, you’ll want to treat the double-strand as though it was one strand. I hope this helps!


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