Yarn weight


Yarn weight refers to the thickness of yarn used by knitters, weavers, crocheters and other fiber artists.

Importance

Changing yarn weight or needle size can have a significant impact on the finished project, so standardized systems have been spread about, as well as conversion systems for regional standards.
Yarn weight is important in achieving the correct gauge or tension for a particular project and can help with yarn substitution. The Craft Yarn Council of America has developed a system that seeks to standardize the labeled weights of yarn. Most yarns state their weight on the ball band but some may not, only giving the composition. Some brands use a standardized numbering system that uses seven ranges of relative thickness of yarn. However there are methods for individuals to gauge weight for themselves.

Wrap method

One way of determining the weight of an unknown yarn is to use the wrapping method. This convenient method is also used to calculate the amount of yarn needed for a project. By this method it is possible to check yarn for sale with a simple pencil and ruler without unwinding the skein, simply slipping the pencil under approximately an inch of the threads and holding a ruler against them.
Wrap the yarn around a large needle or a ruler. Make sure the yarn lies flat. Push the yarn together so there are no gaps between wraps. Smooth it out so it is neither too loose nor too tight. Measure the number of wraps per inch. For better accuracy, measure the wraps at the center of your yarn sample.
The number of wraps will act as a gauge to assess the thickness of unmarked yarn; for example 12 wraps per inch is 12 WPI, and is used to calculate how much yarn is required for various articles, so that 12 WPI is equivalent to 8 ply yarn.

Swatch methods

A more hands-on method, there is the Test swatch and the Gauge swatch. Knitting a Test swatch requires at its simplest, knitting the yarn into a small, roughly 4 in square textile of even stitches. Comparing this with recommended needle sizes, yarn, and the knitter's own signature tension, allows for adjustments to all of these things. For example, changing needle size is one way to bring the test swatch nearer to an accurate measurement in yarn weight.
The Gauge swatch goes further. Not only is it a tool for checking whether yarn conforms to a desired dimension, but it is usually produced with some of the complexities of the intended project making it a much larger test piece. This larger sample is then "dressed" meaning washed, ironed, and subjected to other processes expected of the finished item. It is especially used for items that require a lot of work and time, to avoid dimensional mistakes in the long run.

International standard weights

Below is a table comparing yarn weights in a range of countries—
USAUKAustraliaGermany m/100gWraps Per Inch,Recommended knitting needle size, mm,Recommended crochet hook size, mmOther terms used,
0 or Lace1 plyMore than 80040+ wpi1.5 - 2.51.5 - 2.5Single, Cobweb, Thread, Zephyr
0 or Lace2 ply2 fädig 600-80030-40 wpi1.5 - 2.51.5 - 2.5
1 or Super Fine3 ply3 ply3 fädig500-60020-30 wpi2 - 32.25 - 3.5Light Fingering, Sock, Baby
1 or Super Fine4 ply4 ply4 fädig350-45014-24 wpi2 - 32.25 - 3.5Fingering, Sock, Baby
2 or Fine5 ply6 fädig250-35012-18 wpi3 - 43.5 - 4.5Sport, Baby, 3-ply
3 or LightDK or 8 ply8 ply200-25011-15 wpi4 - 4.54.5 - 5.5Light Worsted, DK
4 or MediumWorsted, Aran, Triple Knit 10 or 12 ply120-2009-12 wpi4.5 - 5.55.5 - 6.5Worsted, Afghan, Fisherman, 4-ply
5 or BulkyChunky, Double Double Knit 12 or 16 ply100-1306-8 wpi5.5 - 86.5 - 9Craft, Rug
6 or Super BulkySuper ChunkyLess than 1005-6 wpi>8>9Roving
7 or JumboLess than 100n/a12.75 mm and larger15 mm and largerRoving

Fabric

The following equation may be used to determine the weight of warp and weft required for a particular fabric:
If there are two colors in the warp, use the following equations:
If the counts of two warps are the same:
or
If there are two colors in the weft:
or
  1. Reed x width / 7000 = Ans
  2. Ans x quantity / count = The weight required