What is yarn weight?

One of the many confusing terms in knitting is “yarn weight”. It has a couple of different meanings, but each influences the other. Hand knitting yarn is purchased in a few different formats, a ball (round), skein (oblong), or hank. Each format is commonly sold in 25, 50, or 100 gram units. This is the actual weight of the ball, skein or hank. Yarn weight also refers to the thickness of the yarn strand, and is categorized as such. Let’s delve into the specifics of each meaning for “yarn weight”.

Yarn Weight Categories

Yarns are produced in a variety of thicknesses, called “weights”. A strand of yarn varies in thickness from very fine to jumbo (a new category). Weights are useful as a guideline in choosing yarn for your projects, particularly when substituting one brand for another. Pattern magazines and other resources like Vogue Knitting and Interweave Knits categorize yarn weights into eight groups, a system devised by the Craft Yarn Council. A numerical symbol is used to identify each category. Each weight group is given an approximate gauge range, as well as the recommended needle sizes. The occasional yarn manufacturer prints the weight category on their yarn labels. The Craft Yarn Council (yarnstandards.com) also applies these same categories to crocheting.

standard yarn weight system

To complicate matters, some yarn producers in the UK and Australia use the number of plies to correspond to the yarn weight categories. This method of categorizing yarns is not accurate or clear in meaning. A yarn can be a single ply or consist of many plies, and belong to any one of the eight categories. The chart below compares the yarn categories between US, UK, and Australia, along with their corresponding names.

comparing yarn weights - US, UK, and Australia

As indicated, each standard weight category provides an approximate gauge, but these are not exact. Every knitter works to a different tension, so it’s critical to rely on the gauge you obtain using a particular yarn and needle size. There is no “correct” needle size, only a “correct” gauge.

Format Amounts

Whether the yarn comes as a ball, skein or hank, they are sold in common amounts or weights of 25, 50 or 100 grams. Although unusual, you may come across different amounts such as 40 grams or 65 grams as in the example of super fine yarn in above image. This is the actual weight of one ball of yarn. Yarn length is the meterage (metres) or yardage (yards) amount that makes up one 25, 50 or 100 gram ball of yarn. The thickness of the strand or weight category described in the last section affects the length or amount of yarn contained in each ball. A bulky yarn will have less meterage in a 50g ball than a 50g ball of light weight yarn. Yarn length is printed on all yarn labels. Pattern instructions indicate in the materials section the weight in grams (ounces), the yarn length for each ball of yarn, and the total number of balls needed for the project.

When buying yarn it is most accurate to calculate yarn amounts according to the total meterage needed for the project, and not by the total amount in grams or ounces. This is because two different 50 gram balls of yarn will have different lengths. A 50g ball of lace weight yarn may be 420 metres in length, whereas a 50g of fine yarn may be 200 metres in length, not to mention that the gauges will be different.

Often, vintage pattern instructions only gave the yarn amounts for a project in grams (ounces), making it difficult to calculate the amount needed. In the past, there weren’t many types of yarns available as there are today, so it was fairly accurate to purchase based on the weight of the ball. Sometimes searching online for an old yarn brand can provide more information including the yarn length per ball.

Yarn weight categories are useful as a guideline to choosing yarn for your projects. The yarn length making up one ball of yarn is key to calculating the correct amount required for a project, and not the amount in grams or ounces. The above information is important when substituting one brand of yarn for another, designing your own projects, and working from vintage patterns.

(Refer to “It’s All About The Yarn” and “The Why and How of Test Swatching” in Resources For Better Knitting for further information on substituting yarns and gauge.)

And if you need a little help with metric and imperial systems – 

conversion factors