What Is Yarn Weight?

If you’re new to knitting, the term “yarn weight” can be slightly confusing. It doesn’t refer to how much the ball weighs—it describes the thickness of the strand.

Yarn weights are useful industry standards that help us understand what to expect from a yarn, from something beautifully fine and delicate to something wonderfully thick and chunky. They also give us a starting point for choosing needles, finding patterns and predicting the kind of fabric a yarn will create.

Here’s our guide to the most common yarn weights.

Lace

Lace is an extremely fine yarn, usually paired with needles between 1.5mm and 2.25mm.

Most mohair yarns are classed as lace weight. Although you can knit with them on their own, it has become increasingly popular to hold a strand of mohair together with another yarn. This adds softness, warmth, colour and a beautiful halo to the finished fabric.

Fingering or 4ply

Fingering weight (USA) —more commonly called 4ply in the UK—is a very fine yarn that creates a light, thin fabric. It is usually knitted on needles between 2.25mm and 3.5mm.

This is the most popular yarn weight for sock knitting, but it is also lovely for lightweight garments, shawls and delicate accessories.

It is worth remembering that “4ply” is now generally used as a weight category. It does not necessarily mean that the yarn has been made from exactly four individual plies.

Sport

Sport is a yarn weight most often found in American patterns. It sits between the fineness of 4ply and the extra substance of DK.

Usually knitted on 3.5mm to 3.75mm needles, sport weight creates a fabric that feels light but not overly delicate. It is a particularly lovely choice for comfortable garments that can be worn through several seasons.

DK or Double Knitting

DK is one of the most popular and versatile yarn weights. It is roughly twice the thickness of 4ply and is most commonly knitted on 4mm needles.

DK strikes a wonderful balance: it creates garments that feel warm and substantial without becoming too bulky. It is equally suited to jumpers, cardigans, children’s clothing, blankets and accessories, making it an excellent all-round choice.

Worsted

Worsted is sometimes described as a heavy DK. It sits between DK and the thicker Aran weight and is normally knitted on approximately 4.5mm needles.

It is a great option for our milder UK winters, creating warm and cosy garments without quite as much bulk as a traditional Aran knit.

Aran

Aran is a classic, substantial yarn weight traditionally associated with richly textured designs full of cables. However, it can be used for almost any style of knitting.

Normally worked on 5mm to 5.5mm needles, Aran yarn creates a warm, sturdy fabric. It is especially well suited to outerwear, winter jumpers, blankets and beautifully cosy scarves.

Chunky, Bulky and Super Chunky

Chunky and super chunky yarns have enjoyed a huge surge in popularity in recent years. They grow quickly on the needles, making them very satisfying to knit and ideal for quick projects.

Needle sizes vary considerably, from around 6mm to 15mm or even larger, depending on the yarn.

These weights work particularly well for scarves, hats, cowls and other accessories. Garments can look wonderfully dramatic, but it is worth remembering that they may also feel extremely warm, bulky and heavy to wear.

“Bulky” is the American term generally used in place of the UK term “chunky”, just as “fingering” is commonly used in place of “4ply”.

Choosing the Right Yarn Weight

The recommended needle sizes above are helpful starting points rather than strict rules. Fibre content, yarn construction, knitting tension and the fabric you want to create can all affect the best needle size for a project.

Always check the yarn label and your pattern, then knit a tension square before beginning a garment. A small amount of preparation can make an enormous difference to the fit and feel of the finished piece.

Once you understand yarn weights, choosing yarn becomes much easier. Whether you want a delicate shawl, an everyday DK cardigan or an irresistibly chunky scarf, the yarn’s weight gives you your first clue as to how the finished project will look, feel and behave.