Hooray! You’ve finished a major knitting project. Then you take another look. Only then do you discover that you’ve knitted it in the wrong kind of yarn. Aaaaahhh!!! You thought it would be beautiful – but it’s anything but. And to make matters worse, it’s cost you a load of money and time.

In this article, I’ll help you find out how to avoid this nightmare scenario. You’ll discover more about the different thicknesses and types of yarn – and why this matters.

These days, there are so many types of yarn available. But what if you can’t get hold of the yarn your pattern specifies? Perhaps it’s not available any more, or you just don’t like the range of colours. But don’t worry. The good news is that there’s always a way round it.

All about yarn weight

The relative thickness or otherwise of yarn is measured in terms of its ’weight’. It’s a little confusing, I admit. This is because it’s not to do with how much your yarn actually weighs. In the past, the thickness of yarn might have been related to its weight per given length. But we don’t need to bother with that now. I’m not here to teach a history lesson! You just need to remember the term. And you need to know that the thickness of a yarn is important. This is because it tells you what size knitting needles you need for your project.

Popular yarn thicknesses or weights

These days, we tend to knit with slightly thicker yarns than in the past. Or, to stick with the word I’ve just written about, we knit with yarns of a heavier weight.

These are the four most popular yarn weights:

Light Worsted – also known as Double Knitting or DK

This type of yarn is usually worked on US size 5-7 needles (3.75mm – 4.5mm).

Worsted – also known as Aran

This type of yarn is usually worked on US size 7-9 needles (4.5mm – 5.5mm).

Bulky – also known as Chunky

This type of yarn is usually knitted on US size 9-11 (5.5-8mm) needles.

Super Bulky – also known as Super Chunky

This type of yarn is usually knitted on US size 11-17 (8-12.75mm) or larger needles.

Please look at the table at the end of this post to find out about other weights of yarn and the needles you’ll need. And for more info, read my post All About Knitting Needle Sizes.

Differences around the world

Wouldn’t it have been easier if we all worked to the same weights and names?

The thing is that many years ago, our countries had much less in common. If you lived in the UK, you probably didn’t ever see American knitting patterns. And if you lived in Australia, you probably didn’t see British ones. This meant that each country developed its own system.

Things have got slightly better, however. If you’re in the UK, knitting needles have been sold in metric size (how thick the needle is in mm) for yonks. (Believe me, it was even more confusing before!) But in case you’ve got some old ones you’ve inherited, help is at hand. Read my post on needle sizes that contains information to help you sort out what’s what.

The important thing to remember is that whatever you do, please don’t let all the different measurement systems put you off. I’ll help you to knit any pattern that you love, wherever it comes from. Because once you’ve sorted out a few things, it’s really very straightforward. And you’ll be able to make sense of any knitting pattern.

Are all yarns of a particular weight the same thickness?

The short answer is no. They’re similar, but not always exactly the same thickness. You need to think of knitting yarn weights more as categories than precise measurements. This differences in thickness are due to two main factors. The first is the the yarn’s fibre content. And the second is the way the yarn has been spun. This means that, for example, a worsted (Aran) weight yarn from one brand may feel thicker or thinner than a yarn from another brand. This is more likely to be an issue if the fibres are different. But sometimes it happens even if the fibre content is the same.

Before you throw up your hands in horror, let me share my favourite knitting website. (I don’t receive anything from promoting them, by the way. It’s just an amazingly useful site – and completely free to use.)

The website called yarn.sub. Once you’re there, you can easily look up pretty much any yarn you like. In fact, I’ve never found a yarn they haven’t recognised. You can then find the names of similar yarns. So if your pattern tells you to knit something in a particular yarn and you can’t find it or just don’t like the colours, help is at hand.

Can I substitute one yarn for another if it’s the same weight?

Sometimes you can – but not always. As I’ve just mentioned, yarns of the same weight aren’t always the same thickness. If you use a yarn with the same fibre content, you aren’t likely to have too many problems. But you do need to check by knitting a swatch first.

But most problems happen when people use a yarn that is the same weight, but made from something different. Fibres all have different properties. And if you choose something too different from the recommended yarn, your project probably won’t look like you want it to.

Even when we talk about wool, we’re not just talking about the fluffy coat from any sheep. There are lots of different kinds of wool you can buy these days. And each of these has its own special feel and look.

For example, Merino wool comes from Merino sheep. Then there’s Alpaca wool, which comes from Alpacas (see a lovely Alpaca above!). It’s warmer than sheep’s wool doesn’t contain lanolin. And you’ve probably heard of cashmere wool. This yarn feels incredibly luxurious. It comes from cashmere goats and is known for being super soft, warm, and lightweight – and rather expensive!

Yarns can also be made out of cotton, silk, linen, bamboo, viscose (made from natural materials like wood pulp), and fibres such as nylon, polyester, and acrylic.

What are most yarns made from?

Lots of yarns are 100% wool, 100% cotton, or 100% acrylic. But many yarns also combine different fibres. Usually, this is to produce a ‘best of both’ fibre. In particular, many yarns combine acrylic with wool. Wool is warm and has a lovely light, natural feel. But it’s more expensive than acrylic, less hard-wearing, and some people find it itchy. I’m one of them! But a 50-50 mix of the two fibres usually produces something pretty nice. It’s good quality and reasonably priced. And even adding just 10% wool to an acrylic fibre can add a touch of class.

One of my favourite yarns is the Debbie Bliss Cashmerino range. Her worsted (Aran) yarn is 55% merino wool, 33% acrylic and 12% cashmere. The cashmere gives it a lovely luxury look but it’s also reasonably hard-wearing and not ridiculously expensive.

If you’re in any doubt about whether the yarn you’ve fallen in love with will work for your project, please just head on over to yarn.sub. As I’ve mentioned, this site can give you some close matches to the yarn recommended for your pattern. But in addition, it explains the sort of differences you might expect if you choose a different yarn. This is so useful. And it also tells you if you need to buy more balls or fewer.

The importance of knitting a swatch

As I said, I don’t think you’ll have much of a problem if you switch a yarn for one of the same weight and fibre content. But it’s always important to knit a swatch.

A knitting swatch is a small piece of fabric that you knit before starting your main project. It helps you check you’re using the right needle size to get the correct number of stitches per inch or centimetre. In turn, this ensures that your finished piece is the size you want it to be. There’s nothing worse than knitting something that comes out way too large or small!

I know knitting a swatch can be a right pain. You want to dive straight into your project, right? But I promise you, knitting a swatch could save you hours of time and a whole heap of money. I speak from experience.

Yarn warning!

Whatever you do, don’t knit a pattern that calls for a wool or wool-mix in yarn made from 100% cotton. The two yarns will have VERY different qualities. Wool and wool-mixes are quite light and stretchy. But a 100% cotton yarn will be quite ‘heavy’ with not much stretch.

Actually that’s why I’d never knit something like a jumper in 100% cotton. It just doesn’t work for me. The yarns often seem lovely when you look at the balls. But I don’t think the yarn works when it becomes a garment. They don’t hang well. And in my experience, they don’t wash well. Even after one wash, your garment might not look that great. It might be you’re a dab hand at that ‘reshape while damp’ instruction! In which case, go ahead – that is just not me. When you’ve spent ages knitting something, it’s annoying when it’s disappointing. So don’t say you haven’t been warned!

The difference between wool and acrylic

I just wanted to say something about the differences between wool and acrylic yarns. Back in the 1970s, acrylic yarns were markedly inferior to wool ones. Yes, they were a lot cheaper. They also came in some nice bright colours. But they felt squeaky and often looked cheap and shiny.

However, these days, there are lots of good-quality manmade fibres around. They are often marked ‘premium’ acrylics. And personally, I’m coming round to them. Mostly, this is because I’ve got pretty sensitive skin and can’t wear wool really close around my neck. This is particularly true for fuzzy yarns like angora and mohair (which I love).

It’s true that items knitted in 100% acrylic don’t always wash brilliantly. But if you wash them by hand and don’t get lazy like me, they should be okay. They’re also really useful for baby clothes and blankets. Personally, I wouldn’t knit something for a baby in wool in it, unless it’s marked baby-friendly and washable.

If you can possibly afford it, try to avoid budget yarn. I’ve experimented with it quite a lot. And, in my opinion, it’s just not worth it. Knitting takes time and effort. And knitting with inferior quality yarn will never produce something beautiful. Some of the premium acrylics are not much more costly than the budget ones. And I think you’ll find it well worth shelling out the extra money.

The most skin-friendly woollen yarn

If you’re talking wool, most of the skin-friendly yarns are made from merino wool rather than standard wool. This is definitely the way to go.

Merino wool is less itchy compared to other types of wool because its fibres are finer and softer. These finer fibres bend more easily when they come into contact with your skin. So they’re much less prickly and itchy! I always opt for merino myself. And thankfully there are ranges around that aren’t any more expensive than standard 100% wool yarns.

Yarn Names & Weights and Needle Sizes

Yarn Weight/Names	Needle Size (US)	Needle Size (mm)
Lace, Cobweb, 2 ply	000-1	1.5-2.25
Sock, Fingering, 4 ply	1-3	2.25-3.25
Sport, Baby, 5 ply	3-5	3.25-3.75
Light Worsted, Double Knitting, DK	5-7	3.75-4.5
Worsted, Aran	7-9	4.5-5.5
Bulky, Chunky	9-11	5.5-8
Super Bulky, Super Chunky	11-17	8-12.75
Jumbo, Roving, Arm Knitting	17 and larger	12.75 and larger