Yarn Systems

Marcy Petrini

October, 2020

“How come, asked Laura, that the sett for this project is 24 epi when the sett from my previous project was 30 epi? They are both 20/2 and plain weave.”

The answer is that the previous project was 20/2 cotton and the current project is 20/2 silk.

But that’s no answer, really. The real answer is: the yarn systems. Just like the measures of length were developed in different places as the metric and the English systems, so each yarn production was limited to a region, and a local system was developed.

Below is the comparison for Laura’s and other 20/2 yarns. Yarns are usually labeled with two numbers; the first generally represents the size or grist of the yarn, the second number represents the ply, the number of strands twisted together. Thus all of the yarns listed below are 2 plies because they are all 20/2. But look at the difference in yards/lb.: the larger than number, the more yards to the lb., the thinner the yarn, the closer the sett.


Yarn 20/2


Warp Sett (epi)



24 - 30

Silk (Spun Bombyx)


24 - 28

Wool (Worsted)


20 - 30



30 - 48


Today we don’t really need to know about the details of the yarn systems. Yarn vendors nicely tell us yards per lb. so we can convert our warp and weft length calculations to the amount of yarn weight we need to purchase. They even give us helpful hints for the appropriate setts.

But how do they get the information? From the yarn systems.

I first learned about the yarn systems from an article by Walter Houser called ”Yarn Counts” that appeared in The Weaver’s Journal, Fall 1983, on page 52. Other information is newer, and I often deduced it from what the vendors list for yards/lb. Tencel®, and other yarns extruded form natural materials, for example, use the cotton count and so does cottolin. But the Houser article gives us the foundation.

The first number is the relationship between length and weight, either weight per unit length or length per unit weight. When the length is expressed in skeins, the actual length of the skein varies with the fiber. Here some of the most commonly used systems:


Yarn System

First #
(for 1 ply)

Conversion Factor

Second #


Skeins / lb.

840 yards (cotton count)


Worsted Bradford

Skeins / lb.

560 yards (worsted count)



Skeins / lb.

1600 yards (run)



Skeins / lb.

300 yards (lea)


Dernier Silk Filament


9,000 meter (Den)

*Tolerance, high and low average



14,400 yards (Spindle)


Novelty yarns




European System




* The tolerance is for silk before being degummed; ready for use is 25% to 30% lighter.


We can use the table above to obtain the same information that yarn vendors give us. Let’s use cotton as an example,

One lb. of a 1 cc (cotton count) yarn by definition is 840 yards long (single ply). This is the standard skein.





(or 1/1)

<------------ 840 yards ----------->

1 lb.


A 2 cc yarn means that 2 skeins (each 840 yarns long) will weigh 1 lb. Thus, a 2 cc yarn has 1680 yards to the lb. (840 yd/skein times 2 skeins). This yarn is half the size of the 1 cc.






<---------------------------------- 1680 yards --------------------------->

1 lb.


In general, the larger the count, the smaller the yarn, since so many more “skeins” (each 840 yards for cotton) have to fit into a pound.

The above statements are true for 1-ply yarn. If we take the 1 cc skein and ply it into 2 strands, the yardage will be half, but the weight is the same. A 1/2 cotton yarn is 420 yards to the lb. The two-ply, of course will be thicker than the 1-ply of the same yarn count, but not double. Jill Duarte (Ply Autumn 2020, page 36) says that a 2-ply handspun yarn is about 1½ times the singles that make it up because of the strands winding around each other. The same must be true of commercial yarn.






<------------ 420 yards ------------>

1 lb.


If we take a 2 cc yarn which has 1680 yards to the lb. and ply it into 2 strands, the yardage will be half, 840, for the same weight, back to the original yardage. The size will also be larger because there are 2 strands, but approximately 1½ times the size of the singles.






<------------ 840 yards ----------->

1 lb.


Let’s use an example from a common yarn, 8/2 cotton.

The “8” means that there are 8 skeins in 1 lb. of yarn, each skein 840 yards:

8 skeins x 840 yards/ skein = 6,720 yards

The yarn has been plied, which we know from the “2”, thus for 1 lb. our yardage is:

6,720 yards / 2 = 3,360 yards /lb.

Which is what we find listed from yarn vendors. Incidentally, mercerization does not change the cotton count.

Since a picture is worth a thousand words, here is a comparison of cottons. The gold is 3/2, the blue is 5/2 and the orange is 10/2, all mercerized. This is what our yarn vendors tell us:

3/2 cotton = 3 skeins x 840 yards/skein / 2 skeins/lb. = 1,260 yards/lb.

5/2 cotton = 5 skeins x 840 yards/skein / 2 skeins/lb. = 2,100 yards/lb.

10/2 cotton = 10 skeins x 840 yards/skein / 2 skeins/lb. = 4,200 yards/lb.




Note that 10/2 cotton has twice the yards/lb. than 5/2 cotton, as we expect.

Next time you purchase yarn, make sure you look at the recommended sett by the vendor and remember that the sett of two yarns with same numerical description won’t be the same if the fiber is different.


Happy weaving!