Breaking the Rules: A Guide to Successful Yarn Substitution

Same colourway, different yarns. Which to choose?

Same colourway, different yarns. Which to choose?

Back in my LYS days a customer came in with a pattern she needed help with. It was a beautiful featherweight sleeveless tunic, shown in an outrageously luxurious 2-ply lace yarn with fine merino wool and a touch of mohair. The bust was decorated with a diamond-shape lace pattern, and the equally decorated hemline fell just above the knees. In the photos the delicate see-through fabric was gently fluttering in the wind, ever so softly caressing the model like the soft summer breeze itself.

The lady absolutely adored the way the pictures looked, but had trouble with choosing a size and reading the lace chart, so I helped her and talked her through the pattern and yardage until she felt comfortable enough to start picking out the yarn.

”I don’t really care what kind of a yarn it is,” she said after looking around for a while, ”as long as it’s fingering-weight and cotton.”

I looked at her with stunned disbelief, and delivered the most epic facepalm in the history of planet knitting. A terrifying silence ensued.


Because there are rules when it comes to yarn substitution, and she insisted on breaking most of them.

Knitting patterns are written for specific yarns — and for a good reason. When designers come up with a shape or a stitch pattern, they swatch with many different yarns until they find one that works best with the vision they had in mind. Alternatively, they start off with a certain yarn and build their design around it. Either way, they pay very close attention to the interaction between the design and the yarn to make sure that the finished garment features the best qualities of both.

Sample rack of handknit garments

Sample rack of handknit garments

So when you’re looking at any knitting pattern, the yarn that the designer used for the sample garment is one they can vouch for to deliver the best results – in other words, results that most resemble what they intended with that design. Choosing that yarn will simply make life and knitting easier.

But obviously, not all yarns are available everywhere, and due to allergies and other sensitivities they can’t always be used anyway.

So if you find yourself having to go with a different yarn than what the pattern calls for, you should try to find a balance between the many different but interacting variables. It may sound intimidating, but in reality all you need is just good old common sense paired with a few basic facts about yarn and fibre characteristics.


The number one thing with matching any yarn with any pattern is gauge — i.e. how many stitches you have for a certain width and height of fabric (usually 4 inches/10cm). All the sizing and other pattern information is based on this number, and in order to knit a well-fitting garment, you need to be able to reach the same gauge as the designer. Advanced knitters can play around and strategize with gauge if they absolutely must use a yarn of different weight, often meaning a complete rehaul of the entire pattern — less experienced knitters should aim for the intended gauge.

But getting the same gauge with a different yarn can be a little tricky, because different yarns behave in wildly different ways, depending on the needles used, the size of the garment and the physical weight of the yarn. Heck, getting the same gauge with the same yarn can be troublesome, sometimes, because our own individual knitting style has such a huge impact on gauge.

Gauge swatch

Gauge swatch

The most surefire way to go is to swatch with a few yarns, if possible, and try to find one that gets you the same gauge the pattern calls for, with needles the yarn manufacturer calls for. This is because the manufacturer usually has extensive knowledge of the characteristics of their yarns, and the suggested needle size is one they have learned works best.

But then again — sometimes you might not be using the yarn for its ”intended” purpose, which means that the suggested needle size may not apply. For example, the suggested needle size of our Tough Love Sock is 2.25mm, because as the name implies, Tough Love is first and foremost a sock yarn. But because of its softness and durability it’s often used for cardigans and shawls as well. For those types of things you would be better off with a 3.5mm or so, because thin sock needles would make a larger fabric too rigid.

That said, the important thing to remember is that if you’re changing your gauge with needle size only, you are changing the characteristics of the entire fabric. If you want to use a fingering weight yarn for a sweater, but the pattern calls for a DK yarn with 22 stitches per 4”, you can probably get the target gauge with bigger needles, but the finished sweater won’t have the same structural integrity as a true DK yarn would create, and it probably won’t wear as well either. Cables in particular need fairly tight stitches to appear crisp and well-defined.

SweetGeorgia Superwash Worsted in Rosebud

Cables in Rosebud cardigan. SweetGeorgia Superwash Worsted in Rosebud

The content of the yarn is also important. Fabric knit with 100% merino wool will drape very differently than cashmere, silk or tencel — that’s why it’s super important to knit a big enough swatch, and possibly block it with weights to simulate how much the weight of the finished fabric itself pulls it down and stretches it when worn. Gauge can change drastically after blocking and in use, which affects all kinds of knit textures, including lace, cables and plain stockinette. If you’re not using yarn that the designer has personally seen to work with that particular garment, testing and blocking your yarn is the only way to make sure the sizing will fit and that all your painstaking lacework won’t turn into a hot droopy mess after a single wear.

Yardage: Getting the Most out of Your Yarn

Yardage simply refers to how many physical yards or meters the finished garment consumed. If you’re getting target gauge as described above, then you should be using more or less the same amount of yards as the pattern. This number is important to know because depending on the structure and texture of the yarn, two yarns with the exact same listed weight and gauge can still have a wildly different amount of yards in the skein. Fluffy woolen yarns tend to run a lot further than their sleek 3-ply worsted counterparts. So if a pattern calls for 6 skeins of fingering-weight woolen yarn, you will almost certainly need more than 6 skeins if you want to substitute it with a regular sock yarn. Also, if you go up or down a needle size to get target gauge, you will probably be consuming more or less yardage than the pattern indicates – meaning you may have some leftover yarn, or not quite enough.

Worsted vs. Woolen yarn

Worsted vs. Woolen yarn

Liisa's Reine Cardigan

Liisa’s Reine Cardigan

A case in point is the Reine cardigan I made a while back. The pattern called for 5 skeins or 250 grams of an airy fingering-weight woolen yarn that runs 275 yards per skein. I substituted it with a DK weight yarn that got me the right gauge and fabric, but it only runs 176 yards per skein, so I ended up using 7 skeins or 350 grams (and being aware of the difference, I had reserved enough). Yardage is pure math and numbers, but still important to keep in mind so that you don’t run out of yarn before the finish line.

Texture: It’s So Fluffy I’m Gonna Die

I’ve mentioned structural integrity and fabric characteristics a couple of times now. They both mean basically the same thing – creating a garment that functions the same way the designer intended time after time, use after use. A sweater that’s meant to be very flowy and drapey requires a different kind of yarn (and gauge, as we’ve seen) than a sweater that’s meant to be very firm and structured.

If a yarn has a fluffy quality to it, such as the addition of mohair or a woolen construction, the individual stitches can ”support” themselves and stand up on their own without the help of a tight gauge. This is because even though the fluff can be quite unnoticeable to the eye, the single fluff fibres lean against and get tangled with each other, creating a slight halo that helps the fabric maintain its shape even after repeated uses. Therefore such yarns can be knit up with fairly loose gauges even though the yarn itself is thin.

Welted Cowl (free pattern from SweetGeorgia)

Welted Cowl (free pattern from SweetGeorgia)

By contrast, a very sleek and slippery yarn (such as Twinkle Sock, a tencel blend that we’ve used for some sock club installments) will produce a waterfall-like drape, unless knit up with small needles and a very tight gauge.

In both cases, getting target gauge with an alternative yarn is not enough — you will need to look at how the intended yarn behaves in the finished sample. It’s not always easy to tell just from the pattern and the pictures, though. Trunk shows and shop samples are great ways of familiarizing yourself with the options before you commit to knitting a larger project.

But at the same time texture offers some extra room for creativity. Another case in point: I really liked the design of the Northern Summer Shawl, but I’m always a little hesitant to make shawls that are not 100% garter — mostly because I’m a lifelong supporter of mindless knitting, but secondly because I really, really hate it when stockinette edges start to flip and curl, which you can only repair by re-blocking the entire piece.

The original sample was made with a rustic 2-ply woolen yarn, but I wanted something drapier and chose an 8-ply fingering-weight yarn instead. And it worked like magic — every time I wear the shawl it basically re-blocks itself, because the weight of the heavier yarn pulls the entire fabric down and prevents the edges from curling. (The same kind of effect can be reached by incorporating beads into the edges, by the way.)

Yarn Material:

Different raw materials have different qualities, a fact closely related to fabric textures mentioned above. There are hundreds of sheep breeds out there, all producing fibre with different amounts of crimp (springiness or bounce) and luster. Then we have all the other furry creatures, such as goats, bunnies and camelids, and plant-based fibres like bamboo, cotton and mulberry silk — not to mention synthetic fibres like tencel and acrylic. All of these fibres behave differently when spun into yarn, and, ultimately, when knit into fabric.

Sock patterns are usually written for merino or BFL blends, because the inherent bounce and stretchiness in those fibres makes sure the socks conform to your foot shape and literally hug your feet. If you try to knit those same patterns with yarns that don’t have that springiness, such as pure alpaca or a merino blend with a high silk content, you’ll find that the finished socks will be very droopy and ill-fitting.

In the same way, other features such as warmth and softness of the finished garment will also be determined by the choice of yarn material. A hat featuring a double-layer brim that’s originally knit with a merino-bamboo blend (fairly lightweight and breathable) can turn into a suffocating sweat helmet if knit with something as warm and insulating as alpaca.

Alpaca Yarn

Alpaca Yarn

Generally, if substituting a yarn, I would keep within the same ”family” of fibres — in other words, replacing a high-crimp wool with another high-crimp wool, or cotton with milk protein, or silk with bamboo. This ensures that your garment will have more or less the same features and structural characteristics as the original one.

Why Should I Care?

None of this obviously matters, if you specifically don’t want the same result as the pattern calls for — like I did with my yellow shawl. You may want a heavy knee-length cardigan to be as fluffy and airy as possible, or you may want to give a delicate lace shawl more structure and drape. Yarn substitutions are a great way to be creative and give new life to trusted old patterns. But in order to succeed and make the finished garment work, you will need to consider at least some of the abovementioned factors when choosing a different yarn — once you know the rules, you can break them with more confidence.

The (Non-Bloody) Aftermath

So why was the lady in my initial story so badly mistaken in her yarn choices?

First, you can’t replace a featherweight mohair-blend yarn, known for its translucency and ability to support itself, with something as heavy and rigid as cotton — without drastically altering the way the finished garment wears. The knee-length style meant that the tunic would have required quite a lot of yardage (even without any sleeves) and such yardage would have inevitably translated into so much weight and drape that the gentle, whispery silhouette she was so infatuated with would’ve never come to life.

Second, while she would’ve been able to get target gauge with a fingering-weight yarn, the translucent effect she was so drawn to would’ve been lost in the denser fabric.

Third, she used the words “I don’t really care”, which around here is cause for incarceration without a trial.

Having educated her on these topics, in my gentle philantrophist (cough) idiom, I kind of assumed the lady to turn around and buy yarn that would truly complement the pattern.

Instead, she bought a bag full of fingering-weight cotton yarn, and we never saw her again.

But I did try, right?

22 Comments Permalink
  • Brenda Castiel

    Great explanation and discussion! I’ve been knitting for decades yet I still learned a lot. Thank you.

  • Carolyn Warren

    This is the most comprehensive article I’ve ever read on yarn substitution. Thank you for posting such an excellent piece!

    I usually use the same yarn the pattern calls for. If I am using a wonderful yarn from my stash, I search for a pattern using the same yarn. I’ve learned that is the best way for me to be happy with the end result, because I am not an expert on all the characteristics of yarn that you have described.

  • Pingback: SGY Roundtable: How And Why (Or Why Not!) Do You Swatch? - SweetGeorgia Yarns()

  • Nalynn Nimsomboon

    Thank you for the article. I found it very helpful. Do you have a pattern for the yellow shawl available? I love it!

  • Montana knitter

    I have a pattern for a great sweater, but calls for knitting with two strands. I have a bulky yarn that comes up with the same gauge, but one strand. What would the affect be if I use just the one strand???

    • Liisa / SweetGeorgia

      Thanks for the question!

      It would depend on what the intended effect of double stranding was. Often patterns call for two strands to get a heathered colour effect (the two strands would be of slightly different colours). Or it might be that the designer simply found a yarn that they liked, and decided to use it doubled in the pattern because no equivalent single-strand yarn was available. Usually designers do mention the reason for double-stranding in the pattern, especially if it makes a significant difference compared to thicker single-strands.

      Without knowing what the pattern is, I’d say it would be fairly safe to use your bulky yarn, but try to find out if there’s a specific reason for the original double-stranding, just to be sure. Happy knitting!

  • Annette Monite

    I have a measurement in sock yarn but I need to know how much that is in sport weight. Does anyone know how to convert 3,200 sock yarn yards to ____ sport weight yards?

    • SweetGeorgia

      It would depend very much on what you are planning to make and the gauge required… what are you making?

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  • chris

    Hi, im knitted a beanie that calls for a 10ply wool/alpaca, 20sts in 4″. I want to replace this with an 8ply wool, 22sts in 4″. I was thinking to increase needle size to obtain correct gauge. How or will this affect the shape in any drastic way?

    • Christine

      Increasing the needle size isn’t a great idea, because you’ll get a looser fabric, making it a lot less weatherproof. You’re better off adjusting the number of stitches.

  • myra freberg

    I want to make this jacket called
    Catherine Jacket that is on Raelry , but don’t want to use the mohair yarn. Any suggestions , even if it is a little heavier, but to heavy yarn? thanks
    Be Sweet Medium Brushed Mohair
    Yarn weight
    Worsted / 10 ply (9 wpi) ?
    10 stitches and 17 rows = 4 inches in Stockinette
    Needle size
    US 11 – 8.0 mm
    666 yards (609 m)
    Sizes available
    One size fits most – Piece measures 67.5″ long x 30″ wide

  • Miriam

    I see a pattern to knit a dress for my 18 months old granddaughter, requiring 6 ply Bambino 25g balls. I only see 4 or 8 ply but can’t see anywhere about 6 ply. What can I substitude for 6 ply? Thanks. Miriam (Australia )

    • SweetGeorgia

      Thanks Miriam, Australia’s 6-ply yarn weight is closest to “sport weight” yarn. Slightly heavier than fingering/sock weight. Hope that helps!

  • dyzajic

    what is boucle yarn and uses?

  • maureen

    I have a pattern that just says Aran weight no gauge etc. I am not sure what to use. It is a crocheted blanket. I am in Canada.

    • Speedwell

      Maureen, I’m an American living in Ireland, and my local yarn shop owner explained to me that Aran is equivalent to worsted weight (look for a size 4 on the label if it gives the yarn size). I find it depends on the yarn; one Aran I have is slippery, limp, and close to DK, and another is a heavy, coarse gray local wool that I have to literally pick bits of straw out of as I work (it is actually exhausting to crochet with). If the pattern gives ounces/yards or grams/meters, look for a yarn as close as possible to that weight/length ratio.

  • Holly Champion

    I’ve been trying to relax more physically while knitting, due to developing sore muscles, which has meant that my yarn tension has loosened. Now I just can’t get gauge on anything without using pin-sized needles. Is going down 2-ply with yarn (e.g. using a similar-textured yarn in 8-ply instead of the called-for 10-ply) an ok idea, or do I need to use the tiny (I’m talking 2mm) needles? Thank you for a great article btw! :-)

    • SweetGeorgia

      Good tension and gauge is so important to knitting, and going down to a 2 mm needle for thicker yarn can be so discouraging and finicky. I would look into alternative ways of holding your yarn that might cause less stress on your hands and muscles. One that has come to my attention lately is Portuguese Knitting. It might help manage both your sore muscles and the yarn tension!

  • Ellen

    Is there a guideline to calculate how much yardage requirements change form one weight to another? For example, a scarf or wrap where gauge can be more flexible, calls for fingering, but I’m going to use DK. How do I determine the yardage needed for the DK? Thanks.