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5 Tips for Yarn Substitution When Crocheting Garments

Updated: Jul 4

We have all been there. Love the pattern…. can’t use the recommended yarn. Maybe you can’t get it in your part of the world. Maybe you just don't like it. Maybe your wallet just doesn't like it. Maybe you’re allergic to that fibre and can only work in acrylics. Maybe you live in Queensland and it’s too hot to work in anything but cotton (people tell me this a lot). Maybe you have yarn in your stash that you have been dying to use and you think would be ideal but not really sure…? How can you tell if the yarn you think you want to use is going to work for that garment pattern instead?


Well, this post is for you!


close up photo of 2 skeins and 1 ball of yarn
The age old question: this one or that one? ...Aahh, my pretties!


Recently I have been branching out trying new yarns. Now that my garment patterns are size-inclusive, I like the idea of being more yarn-inclusive too!


What’s that you ask!? Personal preference aside, stock availability, cost, shipping logistics and exchange rates can make sourcing the one specified yarn difficult for hooksters in different parts of the world. I can’t test a wide range of different yarns for a new pattern, but I can at least discuss 2-3 options that have been used for pattern testing and give some advice about how to decide for yourself. Maybe that makes crocheting what your heart desires more accessible….


I will use Shelley Sweater which is a top-down crochet raglan pull-over graded to 11 sizes as an example as we talk Yarn Substitution TIPS!


For my Shelley Sweater prototype, I used Sweet Georgia Yarns Tough Love Sock, meaning I graded and wrote the pattern using this as the specified yarn. It comes as a skein of 388m/115g and is a blend of 80% merino and 20% nylon which is hand-dyed in small batches of glorious unapologetic colours.


Here are a few progress pics... the pink yarn is a skein of Tough Love sock as described above, and the other smaller balls of colour are a "Party of 5 Set" of Tough Love Sock mini skeins.


a crocheted sample with coloured balls of yarn
Beginning the Shelley Sweater - Sweet Georgia Yarns Tough Love Sock

close up of a crocheted top showing feature raglan line
The Shelley Sweater prototype pre-sleeves





Ok... Here are my tips:



TIP #1: For most reliable results of any project, use the yarn specified in the pattern and here is why:

It’s important to understand what a pattern can tell you and what it cannot tell you. A designer will use a certain yarn for their design, they combine it with a certain hook size, stitch pattern, their gauge etc, and it comes out “like so”. They grade it to various sizes based on its measurements and gauge, write up the pattern and publish it as your guide to make the same.


The pattern sizing and schematic information can ONLY tell you how it should turn out if you use the same yarn, achieve the same gauge, and follow all the instructions. It cannot tell you how big or small, stiff, or saggy it will turn out if you use a different yarn.


We get into assessing various yarn characteristics below, but those who are relatively new to making garments generally get a bit nervous about the finished item not fitting them. The best advice I can give here is to use the same yarn as the designer (choose a pattern where you like the yarn they have used and can source it), then focus on matching gauge when swatching and following the instructions. As you gain more experience, get more adventurous.


Yarn substitution requires some expertise and effort, as we are about to find out:




TIP #2: Yarn weight grading systems are great. Here is why I don’t use them and what I use instead:

A “weight grading system” of yarn is a means of assessing how thick or thin it is with some level of objectivity or measurement.


The Craft Yarn Council has a grading system from Lace (0) through to Jumbo (7) with number coding printed on yarn labels. Here is a screenshot from their website to show what I mean.


a grading system for yarn shown in chart form

On the face of it, this seems awesome. In practice, since the yarn manufacturer assigns their own weight grade to their product, the lines can blur. The yarn weights between Superfine (1) and Light (3) in particular can smoosh into each other which is rather unfortunate as these weights are generally suited to crocheting garments. Not pointing any fingers here, it’s just human variance.


The other factor here is that knitters will assign yarn weight according to number of stitches x rows of stockinette stitch, or just stitches as shown above. Manufacturers may use this to grade it as a particular weight, but this is not aligned to how it performs when crocheting (garments or otherwise - there are just so many different crochet stitches and stitch combinations).


The CYC also note an alternative system often used by weavers to objectify yarn weight called WPI – Wraps Per Inch. It comes down to how many times does the yarn wrap around a rule width of 1 inch? Sounds ok but does this mean 2.54cm or 2.5cm as the rule manufacturer could use either? How much stretch/tension is applied when wrapping the yarn? Some yarns stretch more than others, and some people will apply more tension than others when wrapping. More stretch means pulled thinner means more wraps in the inch. You would (generally) be wrapping with unblocked yarn. A stiff cotton might soften quite a bit when blocked and conform better to the rule after blocking, thereby increasing number of wraps...


Suffice to say I don’t go by the above systems. The system I do use isn’t perfect either, but it is less fuzzy (pun intended – haha!), and I look at it in conjunction with other yarn characteristics that are discussed further below.



To assess yarn weight, I go by metres per gram.

Look at the ball band for yarn information and check how many metres per gram of yarn. How do you figure this out? The ball band will say somewhere how many metres in the ball or skein and how much it weighs – for example 400m/100g. Take 400, divide by 100 to calculate 4m/g. (This is a common weight of sock yarn).

Or maybe it says 85m/100g (= 0.85m/g - this is a bulky 12 ply sort of yarn).

Or laceweight yarn is often around 800m per 100g skein = 8m/g.


Easy and quick to calculate. A thick yarn will have few metres per gram and a thin yarn will have many metres per gram, as demonstrated by these Morris & Sons Empire merino yarn samples below: the Laceweight Empire on the right is uber-fine!


3 balls of yarn
3 weights of Morris & Sons Empire yarn (L to R): 125/50=2.5m/g; 175/50=3.4m/g; 700/50=14m/g

This seems like it’s very similar to the CYC grading at first, but the real benefit is that m/g is an objective measure of yarn length in proportion to its weight averaged over the entire ball or skein and the calculated number immediately gives you a tangible benchmark. Successful yarn substitution is likely when it is within +/- 0.2m/g of the specified yarn.


The caveat is that it needs to be further interpreted in conjunction with fibre content and yarn construction, but it gives a good rule of thumb.


So… if the pattern calls for 3.4m/g yarn, your stash-diving hopes will be quickly dashed when you calculate your coveted squishy balls are 2m/g or 4.2m/g and you can quickly move on to google some other yarn delights with a bit of online shopping. A quantifiable and objective requirement to shop for more yarn! ...You’re welcome, but don’t shop just yet, let’s go through the remaining tips.


BTW, if you haven’t done the math yet, the Tough Love Sock in the Shelley Sweater is 388m/115g = 3.4 m/g (rounded to 1 decimal place), so the previous paragraph is direct advice for this pattern.



TIP #3: Both a yarn’s fibre content and structure affect its performance and suitability.

Metres per gram immediately tells you where a yarn is on the scale of thin to thick, but doesn’t tell you if it’s stiff or squishy, elastic, slippery, slubbed or whatever.


Yarn structure can get quite complex. How smooth or fuzzy it is will influence stitch definition and the visual “look” of the project. You might need to zoom in on images of the specified yarn to see if its tightly twisted, loosely plied, braided, or fuzzed with halo for its construction and how this compares to the specified yarn.


Most twisted yarns are S-twist but very occasionally you might find a Z-twist. An S twist will loosen as you crochet with it and a Z will tighten so this will influence your gauge. Degree of twist will influence the degree of elasticity (more twist means more elastic and resilient properties), but you can only guess as to how much because the bigger influence on its springiness or elasticity is fibre type.


Different fibres vary enormously in their characteristics.


Some quick basics: animal fibres will have some elasticity and plant fibres don’t. Some animal fibres are significantly more elastic than others (merino and other wools pretty much top the list). Plant fibres are not elastic at all, and this allows then to be stretched out of shape (meaning slowly sag and stretch with wear) as they can’t “bounce back”. Equally this inelasticity of plant fibres means a fitted garment in cotton needs to be tailored to the contours of the body (think darts and shaping on a tailored suit) or it will restrict body movement and be uncomfortable to wear.


Cotton fibre produces a more dense, stiff yarn structure than merino for the same m/g and ply structure. The Shelley Sweater pattern uses the 3.4m/g merino blend yarn Tough Love Sock. This photo below shows you what happens when the same person (me) uses the same hook size (3.25mm) to work the same swatch using the same (3.4) m/g weight yarn and the ply structure has a similar level of twist (structure), but the fibre is cotton/acrylic instead of merino/nylon: I used Scheepjes Cotton 8.


2 swatches of crochet
Sweet Georgia Tough Love Sock on top; Scheepjes Cotton 8 on the bottom

The cotton swatch is bigger – significantly bigger because the Cotton 8 is less compressible so the dense, stiff thread doesn’t hug the crochet hook as tightly as you crochet. If you happily hook away and make the whole project in the Cotton 8, it will turn out MUCH larger than intended. That's a big no-go for a good garment yarn substitution as it will not come out to the required size.


The other thing here is the Shelley is intended to have 0-5cm ease – pretty fitted at the bust and sleeves, so this ease makes a tightly plied cotton not a great option even if it did match gauge. If you skipped adding lower sleeves so it stops at the shoulders, you might get away with it. If made with sleeves however, arm movement is likely to pull too much on the bodice and neckline. The photo below shows my second sample WIP in a merino silk blend and you can see how the sleeve changes how the neckline sits. The merino still allows the fabric to flex and move with the body when the sleeve moves with your arm but a cotton would restrict comfortable movement.


a person wearing a half made crocheted garment
The effect of adding the sleeve... This is my 2nd Shelley Sweater sample using a merino/silk blend

The take home here is when making fitted clothes, be wary of substituting cotton for merino. If it’s an oversized garment (has 10-15cm of positive ease or so) or a lightweight stitch pattern then a cotton substitute will work well for movement, but even so you would likely choose a cotton yarn with a little higher m/g (thinner to compensate for its inelasticity) than the original merino in order to achieve gauge.


An example of this working would be my Rabbit Alice Sweater which I made with both Scheepjes Metropolis 75% merino; 25% nylon (200m/50g = 4m/g) and Scheepjes Whirlette 60% cotton; 40% acrylic (455m/100g = 4.55m/g). Had I gone like for like in weight, I would have tried a cotton blend within 0.2 mg/g of the Metropolis, but as just mentioned, Whirlette is a little thinner at 4.55 m/g and achieved gauge. The generous positive ease on the garment (and open stitch pattern) of the main fabric allows both options for a comfortable garment.



Now I totally get that all this detail so far may scare those early on in their yarn journey!


TIP #1 is a good one, as yarn substitution does require a bit of expertise and a brave spirit of adventure.


Much of the yarn weight, construction and fibre characteristics can be interpreted for you by a great website though, which brings me to……




TIP #4: Yarnsub.com

This website is a great start to kick-start what you just learnt in tips 2 and 3. For Yarnsub, enter the specified yarn into the search bar and it will list similar yarns based on weight, construction, and fibre content. It will also tell you if a yarn has been discontinued. Very useful!


Ok, so you can just go to Yarnsub and pick one right!? Not so fast – let’s look at the final and most important tip:



TIP#5: Swatching is the answer. Swatching is always the answer.

Yep, there is no getting past it, you must observe, feel and measure your proposed yarn in action. Swatching is the real test. My photo of the stacked swatches is a good example of why. Not sure how to swatch and block? I have a whole other blog post about it here. Assess your blocked gauge to see if it will work for your project (both for gauge and for desired drape). You may need to go up or down a hook size to achieve gauge. Maybe it’s just not possible to achieve gauge in your substitute yarn.



There you have it. Lots packed into 5 tips for Yarn Substitution when crocheting garments!



SO… coming back to yarn-inclusivity.


I hope this blog post helps you with any crochet garment pattern you are taking on. But it is also useful for the Shelley Sweater!


Here's a quick summary of all my yarn substitution tips:


Choose a yarn of similar fibre composition and construction that is within 0.2m/g of the specified yarn. Then swatch a few times to see if you can achieve blocked gauge with it. If you are brave enough to have gone with a cotton in place of a merino, go a bit higher on the m/g and consider if the movement it allows for (ie. open drapey stitch pattern vs stiff which is something you can only assess when you swatch and block) is suited to the garment you are making (ie. fitted vs oversized).


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Happy stitching!

Susannah (Peppergoose)



These are my opinions regarding yarn substitution based on years of designing crochet garment patterns.

There are no affiliate links in this post.

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