Have you ever got a 12 ply yarn and thought to yourself, “But I don’t see 12 separate strands in this yarn?” Or wondered why an obviously really thick yarn is being described online as 4-ply, whereas you know that 4-ply means a fine yarn? Well, there’s a good reason for that. Over the past 200 years, countries evolved different ways to measure the weight (or thickness) of yarn. And yarn evolved over that time too. All of this led to our current situation, in which your “8-ply” yarn may actually have 16 plies – or only one ply! 

Are you confused? That’s understandable, because it’s all very confusing. We’ll dig in-depth to how we got to where we are today. If you’re not interested in the history and just want to understand how to translate yarn measurements between systems, scroll down to the bottom. We have a couple of tables that will help you do so.

Illustration of nine different yarn weights, from thickest to thinnest. From left to right: Jumbo in a hot pink yarn, 14 ply/Super Bulky/Super Chunky (heavy) in a blue yarn, 14 ply/Super Bulky/Super Chunky (light) in a wine yarn, 12 ply/bulky/chunky in a beige yarn, 10 ply/worsted/aran in a green yarn, 8 ply/double knit/dk in a sky blue yarn, 5 ply/sport in a teal yarn, 4 ply/fingering/sock in an orange yarn and 2 ply/lace in a gray yarn.
Nine different yarn weights. (Technically eight – and the two different diameters of Super Chunky yarn illustrate the variance within categories.)

Why Does “Yarn Weight” Mean Thickness?

In most areas, weight refers to how heavy something is. But in yarn, it refers to how thick a fibre is. This is because, once upon a time, people literally measured yarn by the pound.

In the pre-industrial era, many spinners were paid based on the number of pounds of fibre they produced. Hence, the weight of fibre was originally a quite literal term. Historians Jane Humphries and Benjamin Schneider note in their paper “Spinning the Industrial Revolution” that spinners were generally paid more for spinning a finer yarn. This is not just because a finer fibre took more skill to make. But it’s also because the finer yarn produced more yardage per pound. In other words, the finer fibre was a lighter weight per yard, while a thicker yarn was a heavier weight per yard.

Back to Basics: What is Ply?

When we are talking about materials, the noun “ply” broadly means “one layer of a multi-layered material.” (Hence why “plywood” has its name – because it is made from many layers of wood veneer glued together.) In fibre production, the verb “ply” means to twist together multiple strands in order to make a stronger yarn. Each individual strand is called a ply. 

This gray yarn illustrates the many plies that can be in a yarn. It has 14 individual plies that are first twisted with one other to create 7 plies. Then two sets of two and one set of three are twisted together to create three plies, and then those three plies are twisted together to make the yarn.
This twist on twist yarn shows how complicated plies can be. It has 14 individual plies that are first twisted with one other to create 7 plies. Then two sets of two and one set of three are twisted together to create three plies, and then those three plies are twisted together to make the yarn. This is a 10 ply/worsted weight yarn, but at no point are there 10 individual plies in the construction of this yarn.

How Ply Became a Yarn Thickness Measure

Once upon a time, people spun most yarn out of wool. And, generally speaking, when wool was spun by machine, the fibres were spun to form a thread or ply of one specific diameter for standardisation purposes. If the factory wanted to make a thicker weight of yarn, they would ply together several different strands of fibre. This is how ply became a measure of thickness. It’s because there was a direct relationship between the number of plies, and the finished thickness.

This historical treatment is why most Australian and New Zealand yarns still use ply as a measure of weight. Certain sizes of UK and German yarns also use ply. 

This system never took off in the USA. A browse through early 1900s advertisements reveals yarn weights such as “coarse,” “Shetland floss” and “Saxony.” These and many other terms in use, at least to modern eyes, don’t seem very informative. Some of these colloquial terms that refer to different weights became standardised by practise over time. This means that in the USA, companies often refer to yarn weight using a word, such as fingering or sport. 

And if this seems chaotic to you – it was even worse before the industrial era! Before machine spinning, yarn weight measurement differed from area to area within Britain and other areas. The discrepancies were so vast that in the early factory era, manufacturers had tables to correlate between the many different measuring systems in use. For a deep dive into how measurement systems evolved in this era and their implications for the fibre business, read David J. Jeremy’s 1971 page-turner, “British and American Yarn Count Systems: A Historical Analysis.” (If you are not deeply invested in the history of yarn weights, it’s an effective sleep aid.)

Why is Ply a Problematic Yarn Weight Measure? 

If ply ever was a truly reliable standard (which is questionable), it hasn’t been one for decades. Nowadays, machines can spin fibres to form threads or plies of very different diameters or weights. In fact, chainette and air-spun construction techniques mean that a yarn may not be plied at all. So a very fine yarn could be a single ply, and a very chunky yarn could also be a single ply – and every other combination in between. 

Close up of strands of three single spun yarns of different weights: a hot pink bulky yarn, a purple 12-ply yarn and a teal 5 ply weight yarn.
The top yarn is bulky weight, the centre yarn is 12 ply weight, and the bottom yarn is 5 ply weight. However, all are single-spun.

Ply Affects Other Things Too

But as well as influencing weight, the number of plies and how they are twisted also influences how a yarn performs in the finished project. The number of plies can affect:

  • stitch definition and stitch shape
  • how the finished fabric moves on the bias
  • the strength of the fabric
  • how much it might pill
  • how soft or how dense the fabric might be
  • and other things that you as a knitter or crocheter or fibre artist may care about when choosing a yarn.

A yarn made of 3 plies will theoretically be stronger and more suited to socks than a yarn made of 2 plies, for example. So surely, a good yarn manufacturer will tell you how many plies are in the yarn, right? 

American yarn manufacturers often do so, but NZ and Australian yarns don’t tend to! Probably because it would be too confusing to have two different references to plies on the label. Imagine you are shopping online and you see two yarns labelled “3-ply.” It is entirely possible that one is an American yarn that is very chunky but made of 3 actual plies, and one is an NZ yarn, very fine, but made from only 2 actual plies. 

If you untwist your yarn, you can see how many plies there actually are in it. This may be very different from the “ply” measurement the manufacturer uses. You can also have an 8 ply yarn (by weight) that is much thinner than another yarn with 4 actual plies. It all depends on the fibres involved. So you can see how using this term can get confusing!

Two yarns with four plies of fibre. The top blue yarn is about half the thickness of the bottom red yarn.
4 ply construction in 4 ply and 8 ply weight

Is WPI the Only True Yarn Weight Standard?

Many people will argue that there is only one truly reliable measure of yarn weight, and that’s WPI or “wraps per inch.” This measures how many times the yarn can wrap around a ruler in one inch. While that’s not so useful for those of us who use metric, it does give you an idea of thickness. A yarn with a lower WPI will always be thicker than one with a higher WPI.

The term “wraps per inch” was first used in rubber and rayon industry journals in 1936. The American Society for Testing Materials (now ASTM International) then began using it as a standard for the weight of fibres such as cotton and nylon. The textile industry was the only group using the term until the 1980s. That’s when we see it make the leap to knitting, possibly with home weaving and spinning as the conduit.

However, organisations such as the Craft Yarn Council of the United States argue that WPI is not a good measure. This is because different people wind yarn differently and hold different levels of tension on a yarn when they wrap it. This can cause significant variance.  

If you are looking to substitute one yarn for another, and you don’t want to swatch a yarn, WPI will be your most accurate measure of thickness. But bear in mind that thickness is only one component of substitution. Therefore, the same thickness does not guarantee a good substitute! However, WPI is also fiddly, which is where ply and other weight measures come into play.

The Craft Yarn Council’s Weight Standards Also Have Issues

The Craft Yarn Council of the United States decided to take a page from ASTM’s book by creating a standard for yarn weights. They’ve even translated it into both Spanish and French. But while this was a lovely attempt, it did not necessarily align with the reality of the yarn we use. The good news is that it includes a name for yarn that is even thicker than yarn most knitters and crocheters use. However, their measurement system does not distinguish well enough between some of the lighter weights of yarn. For example, a 3 Ply/light fingering and a 4 Ply/fingering/sock both fall under the “1: Super Fine” category. 

And the Craft Yarn Council doesn’t have an official WPI range definition for these weights. They do offer guidelines for the WPI range for each weight…which they sourced from Ravelry. The Craft Yarn Council argues that WPI is subjective because different people can wrap yarn differently.

Two ply construction in 12 ply (top) and 4 ply (bottom) weight yarns. Image is a close-up of the end of those strands of yarn, with the plies separated.
Two ply construction in 12 ply (top) and 4 ply (bottom) weight yarns.

But Doesn’t Yarn Weight Mean…Weight?

We regret to inform you that, unlike the pre-industrial era, the actual weight of the yarn has no bearing on its thickness. Even in the days before industrialization, yarn weight was not necessarily a reliable indicator of thickness. That’s because the number of ounces in a pound varied drastically based on what country or even which county you were in. (And let’s not even discuss the variance in how much an ounce was.) We have at least now standardised how much a pound or kilo is. But there is no way to standardise how much each type of fibre weighs per metre.

Different fibres have different weights. Alpaca wool weighs more than normal sheep wool but is lighter than merino wool. Silk is lighter weight than wool, and as you may have read in our article about possum wool, possum is hollow and weighs even less than that. Any discussion of yarn “weight” refers only to its thickness, not to the actual number of grams per metre of yarn. This means that two balls of the same thickness of yarn, that weigh the same number of grams, might have very different yardages. Most modern patterns include yardage details to help with substituting yarns for this reason. 

Close up of the ends of two yarns with 3-ply construction. The top teal yarn is in DK weight, and the bottom blue yarn is in 4 ply weight.
Both of these yarns have 3 ply construction, but the top yarn is DK weight and the bottom yarn is 4 ply weight.

How Do We Tell You Stuff On Our Website?

We recognise that people from all over the world shop here. And you might also be using a pattern from a different place from where you are based as well!  To help you, we have all our yarns separated into weight categories. We name each category with both its NZ/Australian thickness classification and the most common American classification.

Each yarn also has the weight in grams included in the specifications. But we call this “ball size” to make it clear that we are referring to the weight-in-grams and not the weight-by-thickness. 

Still unsure? You are always welcome to email us and we can help you out!

All the Common Yarn Weight Measurements

When you are shopping with The Yarn Queen, we list the yarn weight names used in several different countries. This is because we know people are familiar with different naming conventions. But you might want to see how they all stack up! 

Please note that, much like the pre-industrial pound, these measurements are defining a range rather than a specific size. For example, if you had two worsted weight yarns, one could be much closer to DK weight than the other. And the heavier worsted could be closer to chunky than that thin DK. So if you are looking to substitute one yarn for another, you may want to look at other factors too.

Yarn CouncilUSAUKAustralia /
New Zealand
WPIKnit Gauge
4 in/10cm
0 / LaceCobweb1 ply1 ply40+
Lace2 ply2 ply30-4032-34 stitches
1 / Super FineLight Fingering3 ply3 ply20-3032 stitches
Fingering4 ply4 ply14-2428 stitches
2 / FineSport5 ply12-1824-26 stitches
3 / LightDKDK or 8 ply8 ply1-1522 stitches
4 / MediumWorsted, AranWorsted, Aran10 Ply9-1220 stitches
5 / BulkyBulkyChunky12 Ply6-814-15 stitches
6 / Super BulkySuper BulkySuper Chunky5-67-12 stitches
7 / JumboJumbo1-40-6 stitches

And If You Are Using Historical Patterns…

If you are using a very old pattern it can be hard to figure out what yarn weight you should be using, especially because the names can be unique. Fortunately, Kim Brody Salazar, who is legendary in needlework circles, has done the very hard work for us. She’s graciously allowed us to reprint her chart here. And if you have interest in embroidery, you should check out her books!

Historical Needle SizeModern Needle SizeExpected Gauge
and Modern Yarn Type
Typical Historical Yarn NamesPossible Modern Substitutes
(no guarantees)
0.25mm1 ply Cobweb woolCotton thread
UK 240.5mmUS #00000000 (8/0)1 ply Cobweb woolCotton threadSize 80 cotton
UK 220.75mmUS #000000(6/0)1 ply Cobweb woolCotton threadWool FlossSpool CottonKnitting cotton
UK 19US 18 Steel1.0mmUS #00000(5/0)1 ply Cobweb woolCotton threadSize 50-80 cottonJamieson 1-Ply Cobweb Wool
US 17 Steel1.125mm1 ply Cobweb woolCotton thread
UK 18US 16 Steel1.25mmUS #00002 ply Lace weightCotton threadBerlin WoolBriggs Knitting SilkSize 50 cottonSkacel Merino Lace
UK 17US 15 Steel1.5mmUS #0002 ply Lace weightCotton threadBerlin Wool, Andalusian WoolSize 30 cottonSkacel MerinoLace Lorna’s Laces Helen’s Lace
UK 15US 14 Steel1.75mmUS #003 ply FingeringLight Fingering30-32 st = 4 inSaxony, Shetland, Pompador,German Fingering, AllianceJamieson Shetland Spindrift,Brown Sheep Wildfoote, Dale Baby Ull (knit very tightly), Kroy 3-PlyMost of
the lighter weight sock yarns
UK 14US 13 SteelUS 0 Standard2mmUS #03 ply FingeringLight Fingering30-32 st = 4 in4 ply Fingering
28-30 st = 4 in
Saxony, Zephyr,Jamieson Shetland Spindrift; Kroy 3-PlyMost of the lighter weight sock yarns
UK 13US 12 Steel2.25mmUS #1 (some)3 ply FingeringLight Fingering30-32 st = 4 in4 ply Fingering
28-30 st = 4 in
Saxony, Zephyr, CocoonJamieson Shetland Spindrift; Kroy 3-PlyDale Baby Ull (knit very tightly)Most of the lighter weight sock yarnsMost standard sock yarns;Rowan 4 ply yarns
US 1 Standard2.5mmUS #1 (most)4 ply Fingering28-30 st = 4inSaxony, Beehive, PenelopeMost standard sock yarns;Rowan 4 ply yarns
UK 12US 11 SteelUS 2 Standard2.75 mmUS #24 ply Fingering28-30 st = 4 inBeehive, Peacock, PenelopeMost standard sock yarns;Rowan 4 ply yarns
UK 11US 10 SteelUS 3 Standard3mmUS #3 (some)4 ply Fingering 28-30 st = 4inLighter sport weights
25-28 st = 4 in
Koigu; GGH Marathon; ZitronLibero
UK 103.25mmUS #3 (most)Sport weight24 st = 4 inchesLouet Gems Opal Merino; JaegerMatchmaker
US 9 SteelUS 4 Standard3.5mmUS #4Sport weight24 st = 4 inLouet Gems Opal Merin; JaegerMatchmaker
UK 9US 8 SteelUS 5Standard3.75mmUS #5Gansey weight,5-ply23 st = 4 inJumper woolWendy Guernsey 5 Ply
UK 84mmUS #6DK weight22 st = 4 inGermantown, Zephyr, SaxonydoubledJaeger Matchmaker DK; JoSharp DK Wool;Most standard DK weight yarns;Most 4 ply fingering weights, doubled
US 6 Standard4.25mmDK weight22-21 st = 4 inLighter airy worsteds, heavycable spun DKs, most 4 ply fingering weights doubledWhatever can be knit tojust under regulation worsted weight
UK 74.5mmUS #7Worsted20 st = 4 inGermantownCascade 220
US 7 Standard4. 75mmWorsted20 st = 4 in
UK 6US 8 Standard5mmUS #8Heavy worsted19 st = 4 inchesAran
18 st = 4 inches
Most standard Aran weightyarns; Most standard sport weight yarn, doubled;Most standard mass market yarns labeled “Worsted” with on-label gauges of19-18 stitches over 4 inches (10cm)
UK 5 (some)US 9 Standard5.25mmAran18 st = 4 inches
UK 55.5mmUS #9Light bulky17-16 st = 4 in
US 10 Standard (some)5.75mmLight bulky17-16 st = 4 in
UK 4US 10 Standard6mmUS #10Light bulky17-16 st = 4 in
UK 3US 10 1/2 Standard6.5mmUS #10 1/2 (some)Bulky15-13 st = 4 inGermantown doubledTwo strands of Cascade 220;Most standard worsteds, doubled
UK 27mmUS #10 1/2 (some)11Bulky15-13 st = 4 in
UK 17.5mm11Bulky15-13 st = 4 in
UK 08mmUS #11Bulky15-13 st = 4 in
UK 009mmUS #13Super bulky12 or fewer st = 4 in
UK 00010mmUS #15Super bulky12 or fewer st = 4 in
12.5mmUS #17Ultra10 or fewer st = 4 in
14mmUS #18Ultra10 or fewer st = 4 in
15.5mmUS #19Ultra8 or fewer st = 4 in
19mmUS #35Ultra8 or fewer st = 4 in
25mmUS #506 or fewer st = 4 in

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