Systems for sizing yarn fall into two basic traditional types, and a third modern one.

A: The yarn number is based on the ** length** of yarn needed to make up a
**specified weight**. The larger the number, the finer the yarn. Cotton, wool
and linen are numbered with such systems.

B: The yarn number is based on the **mass** of a **specified length**
of yarn. The larger the number, the heavier the yarn. Silk, synthetic fibers and
jute are numbered with such systems.

C: The actual maximum diameter of the yarn is specified.

Many yarns consist of more than one ply. To describe the weight of multi-ply yarn both the number of plies and a yarn number must be given. A fraction is used: two numbers separated by a slash. The first number is the number of plies. The second number is the cut or run number of the yarn as a whole, not of the plies separately. So, for example, 2/10s cut wool yarn would have two plies, and 3000 yards would weigh a pound. In other words, the plies themselves would be 20-cut.

A different format is used for silk.

Yarn number systems by type of fiber

- cotton
- jute, heavy flaxes, coarse hemp
- linen, fine hemp
- mohair and camel's hair
- modern
- ramie
- silk and synthetic fibers
- wool
- worsted
- comparison

In English-speaking countries, the yarn number is the number of 840-yard hanks in a pound. The convention for indicating plies resembles that for wool. Two-ply 20s would be written 2⁄20s or 20⁄2, and would be twice the weight, length for length, of single ply 20s yarn.

On the European continent, the yarn number is the number of 1000-meter lengths in 500 grams.

In the Dundee Jute Count, the count was the weight in pounds avoirdupois of a spindle of 14,400 yards. “If 14,400 yards weigh 8, 10 or 12 lbs. the grist of the yarn is called 8, 10 or 12 lb. respectively.”

In England and the United States, the Irish system, by which the counts or lea number is the number of 300-yard leas in a pound.

Linen has been spun as fine as 400s and even 600s, which are used in making fine lace. To achieve such fineness, Belgian hand spinners worked only in damp basements.

Same systems as used for worsted wool.

Over the years there have been dozens, perhaps hundreds of yarn numbering systems. Many of these are still in active use in the 21st century.

In 1900 a conference was held in Paris in an attempt to reach agreement on a single international standard (the Congrès International pour l'unification du numérotage des fils). They chose method A: the international metric count is the length in meters of 1 gram of the yarn. But they made an exception for raw and thrown silks, for which the yarn number is the weight in 0.05 gram chunks of a 450-meter length. So, for example, if a 450-meter length of silk weighed 1.5 grams, its yarn number would be (1.5/0.05) 30.

Many years later another international unit was developed, one based on method B. This unit, the tex, is the weight in grams of 1 kilometer of the yarn.

In England, the count was the number of 300-yard hanks in an avoirdupois pound.

On the continent, the count was the number of 1000-meter hanks in 1 kilogram.

Synthetic yarns other than glass, and raw and thrown silk yarns are sized by the metric and denier systems.

The metric yarn number, or legal denier count, is the mass in grams of a 450-meter length of the yarn divided by 0.05, or, another way of saying the same thing, the mass in grams of a 9000-meter length. Adopted in 1900 by the Congress in Paris mentioned above.

The denier was a French coin, = ^{1}/_{12} of a sou, whose
mass was used as a weight in calculating yarn numbers. In Great Britain and the
United States, denier was originally applied only to raw silk. Being a natural
product, silk varies in thickness, so the size is usually given as a range, for
example, “^{13}/_{16} denier.”

Some old denier systems, with the international for comparison:

“international” denier | mass in grams of a 500-meter length ÷ 0.05 |

Turin denier | mass in grams of a 474-meter length ÷ 0.05336 |

Milan denier | mass in grams of a 476-meter length ÷ 0.0511 |

Old Lyonese denier | mass in grams of a 476-meter length ÷ 0.5311 |

New Lyonese denier | mass in grams of a 500-meter length ÷ 0.05311 |

The Manchester dram system, or English dram system, was formerly used for thrown silk. The yarn number is the weight of a 1000-yard skein in drams. Nowadays the denier is used for everything.

In the Yorkshire ounce system, also formerly used for thrown silk, the size is the number of yards in 1 ounce avoirdupois.

Spun silk yarn, which is made from leftovers after filament silk has been produced, is numbered by a different system in the United States and the United Kingdom, one like that used for cotton. The yarn number is the number of 840-yard lengths (a hank) in a pound. The smaller the number, the heavier the yarn.

Unlike cotton, the count in a fraction representing multi-ply yarn describes the finished yarn, not the plies.

The yarn number is the number of 300-yard hanks needed to make up a pound.^{1}
Thus 600 yards of 2-cut yarn weigh a pound. Symbol, N_{ac}. In practice
coarse yarns are typically five-cut to seven-cut, medium 18-cut to 21-cut, and
fine yarns 30-cut to 35-cut.

Used around Philadelphia.

1. *ASTM Standard D-123-03. Standard Terminology Relating to
Textiles.*

Edition approved 10 February 2003.

The yarn number is the length in yards of one pound of the yarn, divided by
1600. Symbol N_{ar}. This is the same as the weight in ounces of 100
yards. So one pound of number 1 run yarn is 1600 yards
long, one pound of number 2 run yarn is 3200 yards long, and so on. Numbers 1
through 3 are coarse, 3½ to 5 are medium, and numbers 6 to 8 runs are fine.

Lederer^{1} says a run was 1644 yards and quotes a
1734 Connecticut law that speaks of yarn that is “eight runs to the
pound.”

1. Richard M. Lederer, Jr.

*Colonial American English. A Glossary.*

Essex, Connecticut: A Verbatim Book, 1985.

Page 200.

Bradbury says the yarn number is the weight in grains of 50 yards. US Conditioning and Testing says of 20 yards.

The yarn number is the number of 300-yard cuts in 24 ounces avoirdupois. In practice, it is more easily measured as the number of 200-yard units in 1 pound avoirdupois, which is the same thing.

The yarn number is the number of 300-yard cuts in 26 ounces avoirdupois.

The yarn number is the number of 320-yard hanks in 1 pound. This is equivalent to the number of 20-yard lengths of yarn in 1 ounce.

Originally the yarn number was the number of skeins of 1,536 yards each, in
one

warten. (A warten is 6 pounds.) Eliminating the warten, this is the
same as the number of 256-yard skeins in a pound. Since there are 256 drams in a
pound, the yarn number is also the number of yards which weigh 1 dram.

The yarn number was the number of drams that 80 yards weighed.

The yarn number is the number of hanks, each of 2200 Berlin ells, in 500 grams.

Worsted is wool that has been carded and combed until the fibers are parallel. Generally, only very high quality wool is worth this level of effort.

In English-speaking countries the count is the number of 560-yard hanks in a pound. A pound of 2-count yarn is thus 1120 yards long.

On the Continent, the count is the number of 1000-meter hanks in 1 kilogram.

The values of the Super scale were chosen to approximate the count numbers from the older “number of 560-yard hanks in a pound” system.

The difference between the Super designation and the plain S, e.g., “180's” and “super 180's,” is that the plain s number may be used on any fabric that is at least 45% wool. The Super designation is reserved for fabrics made with new wool. There are two exceptions: 1) for blended mohair, cashmere, alpaca or silk yarns and 2) if the blend is to achieve decorative effects, as much as 5% of non-wool yarn may be added.

In the United States, these specifications are made legal requirements in the Wool Products Labeling Act of 1939 (15 U.S.C. § 68)

Designation (as, e.g. "80's" or "Super 80's") |
The average diameter of the wool fiber must not exceed (in microns) |

80's | 19.75 |

90's | 19.25 |

100's | 18.75 |

110's | 18.25 |

120's | 17.75 |

130's | 17.25 |

140's | 16.75 |

150's | 16.25 |

160's | 15.75 |

170's | 15.75 |

180's | 14.75 |

190's | 14.25 |

200's | 13.75 |

210's | 13.25 |

220's | 12.75 |

230's | 12.25 |

240's | 11.75 |

250's | 11.25 |

International Wool Textile Organization.*Arbitration Agreement and Other International Agreements (Blue Book)*.

Appendix 2: Fabric Labelling Code of Practice; Quality Definitions Relating to "Super S" and "S" Descriptions.

Brussels: International Wool Textile Organization, annual.

1

There are five different French systems for the numbering of worsted yarns: The metric system, measuring 496 yards per pound; the new Roubaix, 354 yards per pound; the old Roubaix, 708 yards per pound; the Reims, 347 yards per pound and the Fourmies, 352 yards per pound.

Louis Harmuth.

*Dictionary of Textiles.*

New York: Fairchild Publishing Co., 1915.

The first
("metric system") is simply the number of 1000 m lengths in 1 kg, converted to
English units. What the original definitions of the other four systems are we
know not.

The following table gives some very approximate equivalents, by weight, for the various systems.

denier | worsted | cotton | woolen (run) |
linen (lea) |
tex | metric |
---|---|---|---|---|---|---|

10 * | ||||||

50 | 160 | 106 | 56 | 298 | 5.6 | 180 |

75 | 106 | 71 | 37 | 198 | 8.3 | 120 |

100 | 80 | 53 | 28 | 149 | 11.1 | 90 |

150 | 53 | 35 | 19 | 99 | 16.6 | 60 |

200 | 40 | 27 | 14 | 74 | 22.2 | 45 |

300 | 27 | 18 | 9.3 | 50 | 33.4 | 30 |

400 | 20 | 13 | 7.0 | 37 | 44.4 | 22.5 |

500 | 16 | 11 | 5.6 | 30 | 55.5 | 18 |

700 | 11.4 | 7.6 | 4.0 | 21 | 77.7 | 12.9 |

1000 | 8.0 | 5.3 | 2.8 | 15 | 111 | 9 |

1500 | 5.3 | 3.5 | 1.9 | 10 | 166 | 6 |

2000 | 4.0 | 2.7 | 1.4 | 7 | 222 | 4.5 |

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Last revised: 15 April 2011.