If you’re new to crocheting and knitting, understanding yarn weights can seem like another confusing topic to learn about.
The reality is, however, that thread weights can be very important.
This is especially true when your pattern needs to be an exact size, such as with a garment.
In this post, I’ll give you the basics of understanding yarn weights so your next project turns out just right.
How is yarn weight measured? What determines yarn weight? Yarn Weight Categories Yarn Weight Standards CYC0 Lace1 Super Fine2 Fine3 Light4 Medium5 Bulky6 Super Bulky7 Jumbo Yarn Weight Symbol Chart How do I know what weight my WPI yarn is? Measure yarn weight in “wraps per inch” What does Ply mean? How does ply affect yarn weight? Ply vs.
WPIEChoose the right weight of yarn for your project Choose the right hook and needle size Why yarn weight is important Gauge Make multiple yarn weights FAQ: Are all yarns in the same weight category exactly the same weight? Even more about yarn crafts
Understand thread weights
Walk down the aisle of your local craft store and you’ll soon see that thread comes in a wide variety of thicknesses, from super-fine lace threads to super-thick jumbo threads.
These different thread thicknesses are organized into categories, called thread weights.
Generally speaking, yarn is divided into seven different yarn weight categories labeled with the numbers 0-7.
These categories are (from 0 to 7): lace, super fine, fine, light, medium, bulky, super bulky and jumbo.
Knitting and crochet patterns are designed with a certain weight of yarn, so it’s important to buy the right type.
When you buy yarn, you can find the weight category of the yarn written on the yarn label.
What determines yarn weight?
The weight of a yarn is determined by measuring the diameter (or thickness) of a strand of yarn.
The most common way to measure the diameter of a thread is with a method called wraps per inch or WPI.
WPI is exactly what it sounds like: take a strand of yarn and wrap it around a ruler until it covers an inch.
The number of times the yarn wraps in one inch is the WPI.
For example, if your yarn wraps around the ruler ten times in one inch, then your yarn has a WPI of 10.
Yarn weight categories
To help crafters select the right yarns for their projects, the Craft Yarn Council has established a system of guidelines that yarn manufacturers use to categorize their yarns.
The CYC standard yarn weight system has seven different categories, numbered from 0 to 7.
Lower numbers indicate lighter yarns, while higher numbers indicate heavier yarns.
CYC yarn weight standards
Below are the categories and types of yarn in each category as indicated by the CYC (Craft Yarn Council).
Lace threads are the lightest weight of threads and are typically used for delicate projects such as doilies, shawls and intricate lace patterns.
Super fine weight yarns are also known as fingering weight or baby weight yarns.
They are slightly heavier than lace yarns and are typically used for projects such as socks, baby clothes and lightweight scarves.
Fine weight yarns are also known as sport weight yarns.
They are slightly heavier than super fine weight yarns and are typically used for projects such as sweaters, hats and other lightweight garments.
Lightweight yarns are also known as DK weight or double knitting yarns.
DK yarns are slightly heavier than fine weight yarns and are typically used for projects such as sweaters, hats, scarves and baby clothes.
Medium weight yarns are also known as worsted weight yarns or aran yarns.
They are slightly heavier than lightweight yarns and are typically used for projects such as afghans, sweaters and hats.
I often think of weight yarns as “all-purpose” yarns, since you can use them for so many different types of projects.
Bulky yarns are also known as chunky yarns.
They are heavier than worsted weight yarns and are typically used for projects like sweaters, hats, scarves and blankets.
Super bulky yarns are some of the heaviest yarns and are typically used for projects such as hats, scarves and blankets.
It is easy to learn how to knit with very bulky yarn, as it is very easy to see the individual stitches.
Jumbo weight yarns are the heaviest weight of yarn and are typically used for projects such as accessories and home decor projects such as blankets.
This type of yarn is also used for arm knitting projects.
Yarn weight symbol chart
In addition to the names given to each category, the Craft Yarn Councils have designed a set of symbols to indicate yarn weight.
These symbols can be found on the thread labels of most commercially available threads.
The chart below shows the seven different CYC yarn weight categories, along with their corresponding names, WPI, gauge, suggested needle and crochet sizes, and symbols.
How do I know what weight my yarn is?
You can usually determine the weight of yarn by reading its label.
Search for a number (0-7) or weight category name.
Whether you threw away the tag by accident or inherited yarn from your grandmother, if you do it long enough, you’re bound to come across untagged yarn.
You can figure out any yarn weight using the wraps per inch (WPI) technique.
As mentioned above, WPI (wraps per inch) is a common way to determine the weight of a yarn.
Whether your thread is missing a tag or you simply want to check that the tag is correct, using the WPI technique is easy and only takes a minute or two.
How to measure yarn weight in “wraps per inch”
To measure your yarn with WPI, you will need a WPI ruler or tool.
Then take your yarn and wrap it around your ruler or WPI tool.
Continue wrapping until the wire supports cover an inch of the tool.
When you’re done, count the number of wraps that fit in one inch.
Compare the number of wraps per inch with the chart above to determine the yarn weight category.
For this reason, it is always important to prepare a gauge sample before starting a project.
super bulky yarn at 5 WPI
super fine thread at 18 WPI
When talking about yarn weight, you’ll often hear terms like 4-ply yarn, 8-ply yarn, or 10-ply yarn.
These terms refer to the number of threads that are broken to make the yarn.
In other words, ply is a measure of how many strands of yarn are used to make one skein of yarn.
A two-ply yarn is made of two strands twisted around each other.
This super bulky yarn has 3 layers.
How does ply affect yarn weight?
In general, the higher the layer, the thicker the thread.
However, it is important to note that the layer does not necessarily correspond to the weight or thickness of the yarn.
Some very thick yarns are only double ply (ie have two thick strands).
Layer is different from wraps per inch (WPI).
WPI measures how many times a strand of yarn can be wrapped around an inch-long object, such as a pencil or ruler.
Ply measures how many strands of yarn are used to make one strand of yarn.
Choosing the right thread weight for your project
When choosing the right weight of yarn for your project, there are a few things to keep in mind.
The type of project you want to make will influence the weight of yarn you should use.
For example, lightweight yarns are used for delicate patterns, such as shawls and socks.
Medium weight yarns are often used for sweaters and hats.
And thicker yarns are often used for projects like chunky blankets and pillows.
Choosing the right hook and needle size
After deciding on the weight of yarn you’ll need for your project, you’ll need to consider what size hook or needle you’ll use.
In general, smaller hooks and needles are used for lighter yarns, while larger hooks and needles are used for heavier yarns.
You can find recommended sizes in the yarn weight chart above or in this detailed crochet chart and comparison guide.
You can also find recommended hook and needle sizes on the yarn label.
Tip: Recommended hook and needle sizes are just that: recommendations.
Depending on how tight or loose you knit or crochet, you may need to use a different size hook or needle to get the same gauge as the pattern designer.
Take a gauge sample and then decide if you need to size up or down.
Why does yarn weight matter?
Sometimes you can get away with not worrying about your thread gauge or weight.
Some projects like blankets, scarves, and hot pads will likely be just as functional, even if they end up a few inches larger or smaller than expected.
When making other items, like socks and sweaters, you’ll want the finished measurement to be exact.
For projects like these, you’ll need to choose the correct yarn weight and needle/hook size to meet the gauge.
Imagine you are knitting or crocheting a 1 inch square.
With thick yarn, you may only need 3 or 4 stitches to measure 1 inch.
On the other hand, if you are working with very thin yarn, you may need 8 or 9 stitches to measure 1 inch.
That’s why it’s important to look at the thread weight suggested by a pattern and always do a gauge swatch before you start.
Yarn weights are also important when using more than one type of yarn for a project.
For example, if you’re making squares for an afghan, you’ll need each square to be exactly the same size, regardless of the yarn used.
To ensure consistency, you need to have a basic understanding of yarn weights.
Frequently Asked Questions About Thread Weights:
Here are some answers to frequently asked questions about understanding yarn weights.
Are all threads in the same weight category exactly the same weight?
Weight categories are very useful for grouping different yarns.
However, just because two yarns are in the same weight category does not necessarily mean that they are exactly the same weight.
In fact, there can be significant variations even within a weight category.
The best way to find the weight of your yarn is by reading the yarn label or measuring its WPI.
And again, if you’re making a piece or other project that needs to be an exact size, be sure to create a gauge sample before you start.
Is aran yarn the same as stuffed yarn?
Both Aran yarns and stuffing yarns are considered medium weight.
Although they look similar, they are actually two different yarn weights.
Fish weight yarn is slightly thinner and finer than Aran yarn.
Aran weight yarn is generally a bit thicker.
Again, though, if finished size is important, be sure to do a gauge sample before substituting one for the other.
How do you replace yarn weights?
The best way to replace yarn weights is to use a yarn that has the same WPI.
This ensures that your finished project will be the right size.
But what should you do if you’re at a craft store and can’t get the yarn out to check its WPI or knit a gauge swatch?
In this case, the easiest way to choose a replacement yarn is to check the yards per ounce (meters per gram) shown on the label.
If the yardage/oz (meters/g) measurement of the new yarn matches the yarn requested in the pattern, it will probably be a good substitute.
Tip: When replacing threads, you’ll want to stick with the same type of fiber.
This way, the yarn will still have the same characteristics that are needed for your particular pattern.
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