How to substitute a yarn's fiber

Published on April 3, 2019 5 min read

If you are substituting a yarn for a new project, it’s important to get it right. In this handy guide, learn how to substitute yarn fiber by exploring how different fibers behave. 

When casting on a new project, it’s not unusual for knitters to substitute yarn. Whether you’re diving into your stash to use up something you already have, or you have your eye on a new spring line of yarn, it’s important to take some factors into account when substituting yarn.

Different stretch, drape, and stitch definition can drastically change how something will knit up, even when you’re using the same pattern and needles. While this guide will help you learn how to substitute yarn fiber, please remember to always knit a swatch before you cast on your project.

Fibers that stretch

Some fibers have more stretch than others. If your pattern calls for one of these fibers, you should try to substitute with another one of these fibers. Another option is to use a blended fiber yarn (I say again: knit a swatch!)


Wool is the trusty sidekick of most knitters. It’s the most popular and widely available fiber to knit with, and it comes in every weight and color that a crafter can imagine. Though there are many different breeds of sheep that produce wool of different qualities, the main characteristics are the same.

Wool is stretchy, warm, and relatively lightweight, which makes it a fantastic choice for garment knitting.

Wooly wonders

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Alpaca fiber is heavier than wool, and can be much warmer. It’s a great choice for winter accessories – it’s affectionately known as “poor knitter’s cashmere" because it’s extremely soft, warm and affordable. Like any fiber, there is a wide range of styles, weights, colors, and prices.

Our alpaca picks

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Cashmere is the upper crust of yarn fiber. It’s unbelievably soft, incredibly warm, and an absolute delight to knit with. It has a similar stretch and drape to wool, but cashmere is softer and lighter in weight. This fiber comes from the undercoat of cashmere goats, and is more than three times warmer than sheep’s wool.

Cashmere stash-builders

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Mohair is very fun to knit with – the “halo” characteristic means that you can use much bigger needles than usual. This quality also means that it can be difficult to substitute mohair as a fiber, and extreme caution should be used when attempting to use it as a substitute.

Mohair fiber has a nice stretch and sheen, which is why it’s known as the “diamond fiber”. These fibers are shorter than other animal fibers, and are usually blended with another for strength and versatility.

Mohair, mo' yarns

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Not-so-stretchy fibers

Generally, plant based fibers do not stretch as much as animal fibers, unless they are blended with polyester, elastane, or acrylic. This is thanks to the cellular makeup of plants, with their rigid block-like formations.

Plant fibers can be distinct from each other, and so substitutions greatly depend on an individual yarn.


Cotton is a familiar fiber to most yarn crafters: most of our everyday clothing is made of cotton, we sleep on cotton, and we use it in almost every application in our lives. As a fiber, cotton does not have much stretch (the clothes we wear are typically blended with lycra to give it stretch). Cotton yarns can be mercerized, which is a heat treatment that allows for brighter colors, a subtle shine, and less chance of breakage or splitting as you knit. Non-mercerized yarns can be softer against the skin, with a clearer stitch definition.

Our cotton collection

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Linen fiber comes from the flax plant, and can be difficult to manufacture. Linen is renowned for being the ultimate in warm weather knitting for its absorbency and lightweight nature. Many yarns blend linen with another fiber for versatility, but 100% linen yarns are not uncommon. Like cotton, linen doesn’t offer much stretch, and it has a light drape.

Linens we love

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Bamboo yarn has a negligible stretch, but a heavy drape. Bamboo has a tendency to stretch out, but not stretch back in – which makes for a fabulous scarf and shawl fiber, but a tricky one for garments. Many yarn companies blend bamboo with other fibers to give it a more versatile stretch with the extreme softness of the bamboo. It has a subtle shine and a supreme stitch definition that’s perfect for accessories and fancy lace knitting.

Bamboo can usually be substituted with cotton, but knitting a swatch is always necessary.

Beautiful bamboos

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Yarns that might be stretchy

Man-made yarns have a wide range of stretch depending on the fiber and construction of the yarn. The best way to be sure when using an acrylic yarn to substitute, is to read reviews on the yarn and sneak a peek at how much twist the yarn has. More twist usually means more stretch, whereas less twist means a more rigid yarn.


Acrylic fibers are generally machine washable and resistant to shrinking, both characteristics that some knitters can’t do without. Most acrylic yarns are created to be of comparable softness, warmth, and stretch to wool yarns, but I (again) emphasize the importance of knitting a swatch!

While acrylic fibers are economical and low-maintenance, they are not biodegradable.

Amazing acrylic yarns

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Yarn crafters love metallic yarns for the shine and sparkle that they bring to projects. They are typically spun with synthetic materials like viscose, polyester, or polymide. These yarns have little to no stretch unless blended with another stretchier fiber, and they don’t typically have much drape. It would be unusual to knit a garment solely using a metallic yarn – they are generally double stranded with something else.

Note: even double stranding a metallic yarn with a stretchier yarn can affect gauge!

Magical metallic yarns

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It would be unusual to find a 100% nylon yarn – instead, nylon is added to other fibers to increase durability and 'washability'. For example, most high quality sock yarns include nylon to fight off wear and tear caused by regular usage.

Yarns with a hint of nylon

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Other factors to consider when looking for substitutes

Beyond stretch, there are a few more things to consider. While stretch is most likely to affect gauge and fit of a garment, there are other issues that can crop up when substituting yarn.

stack of paintbox chunky pots swatches


If you’re knitting something for a baby, hand-wash only fibers might not be the best choice. Conversely, when knitting an accessory, washability isn’t as much of a factor. 


Though I’ve mentioned drape in this post, it has more importance than some realize. The drape of a fiber can make or break a lace knitting project, so it’s important to try it out before you cast on.


Some fibers are warmer than others, and that can affect the versatility and wearability of a garment. Knitting a sweater in 100% alpaca yarn is a great idea for someone who is always cold, but not necessarily a good plan for someone who doesn’t need as many layers to keep warm.

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