Yarn weight conversion chart and beginner’s guide

Want to know the difference between DK and aran weight yarn? Need to choose the right needles for the yarn you've bought? We've got all the information you need right here!

Yarn weight conversion and beginner's guide

About to buy some yarn? Read this first! We’ll explain why a yarn’s weight has nothing to do with grams or kilos, reveal what is meant by fingering, sport and worsted weight yarn, and help you choose the right yarn for your project with our yarn weight conversion chart.


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What is yarn weight?

When choosing the right yarn for your project, size matters. Knitting yarns come in a wide range of different thicknesses, or ‘weights’, and the weight of yarn you choose will have a big impact on the look and feel of your finished fabric. To get the best results it’s a good idea to use the weight of yarn specified in your pattern, although tools such as YarnSub can help if you want to find a substitute. Take care not to mix different weights of yarn in one project, unless it’s a novelty look you’re after!

As a yarn’s weight is determined by its thickness, a thin yarn such as lace is described as ‘light’, while a thick yarn such as super-chunky is ‘heavy’ – regardless of the overall weight of the ball. Yarns come in a range of standard sizes (the most well-known being set by the Craft Yarn Council), which can be found written on the ball band along with the suggested needle size and tension. You can find our guide to these weights below.

What does ply mean?

Ply refers to the number of strands that are plied, or twisted together, during spinning to create a single strand of yarn. A 2ply yarn has two strands, a 3ply has three and so on. If you’ve ever untwisted or split your yarn while knitting, you’ll have seen these individual plies.

Historically, yarn weights were named after these numbers, so the higher the ply the heavier the yarn, but today it’s more complex than that. A 4ply yarn might not have four plies – it could have more or fewer. And a singles (1ply) yarn could be lace weight, big or somewhere in between. Plies are still commonly used as names for yarn weights, particularly in the UK and Australia, even though weight and ply are no longer always related!

What yarn weights are there?

Here are the yarn weights you’ll most commonly encounter in the UK, and our recommendations for what to knit with them.

1, 2 and 3ply

Knit on 2 to 3½mm needles. Use for delicate lace knitting and baby garments. Good for socks and gloves.

1, 2 and 3 ply yarn


Knit on 3 to 4mm needles. Great for baby clothes, heavier socks and lightweight tops.

4ply yarn

Double knitting (DK)

Knit on 3½ to 4½mm needles. Usually double the weight of 4ply, this is the most widely used weight. Suitable for most garments and quick to knit up.

Double knitting DK yarn


Knit on 4 to 5½mm needles. Originally created for fishermen’s jumpers. Use when DK isn’t heavy enough, and chunky is too bulky. Perfect for outdoor or warm clothing.

Aran yarn


Knit on 5½ to 7mm needles. Associated with outdoor wear and winter jumpers, great for oversized garments.

Chunky yarn

Super chunky

Knit on 7 to 12mm needles. A great weight for beginners, as it produces quick results. Good for furnishings.

Super chunky yarn


Knit on 9 to 20mm needles. Perfect for eye-catching scarves and coats, as well as cosy cushions and throws.

Big yarn

Or print out and keep our handy yarn weights chart:

Yarn weight guide UK terms

What is fingering weight yarn?

The yarn that UK knitters will be familiar with as ‘4ply’ usually goes by the name ‘fingering’ in the US. You might also see it referred to as ‘sock’ or ‘baby’ weight because – you guessed it! – it’s an ideal weight for socks and baby garments. It’s generally knitted on size 3-4mm needles and is a popular choice for lace shawls as it knits up into a light but cosy fabric.

What is sport weight yarn?

If you’re looking at US yarn brands or patterns, you might see sport weight yarn mentioned. There’s no direct equivalent in the UK as sport weight sits between two categories: heavier than 4ply but lighter than DK. As a result you can generally use it as a substitute for both weights, but make sure you swatch, swatch, swatch first with knitting tension squares to check that your tension is a good match!

What is worsted weight yarn?

This popular yarn weight (it’s reportedly the most-used yarn in the US) is equivalent to UK aran. Worsted weight yarns are medium thickness and knit up on 4-5½mm needles, making them a good choice for beginners and winter knits such as jumpers and blankets. Light worsted is the same as DK in the UK.

Note that the term ‘worsted’ can also refer to the way the yarn is processed – it can either be worsted spun or woolen spun – so you may see it used in the context of yarn manufacturing and spinning as well.

Yarn weight conversion chart

Yarns come in a standard range of sizes, but the names can vary from country to country. Here’s our at-a-glance guide to the most common yarn weights in the UK and US, and the needles to use with them:

Needle size
Double knitting
Light worsted
Super chunky
Extra bulky

Or print out and keep our handy yarn weight chart:

Yarn weight chart UK US conversion

If you’re new to knitting, patterns can look like they’re written in another language. But don’t worry, we’re here to translate! Whether you’re on your first project or just need a quick refresher, check out our knitting abbreviations for the common stitches you’ll find in our patterns. From ‘alt’ to ‘yo’, it’s all there…

Knitting abbreviations

Now that you’ve mastered yarn conversions find a project to work on with our knitting patterns collection, and see our guides to the best knitting kits for beginners and knitting books for more inspiration.