There are several reasons why a knitter might choose to use a different yarn from the one specificed in the pattern. Perhaps the yarn has been discontinued, or maybe the yarn is outside your budget or you might even already have a large stash (*cough* – like me) that you want to use something from that instead of buying new yarn.

So how do you choose a substitute yarn?

New knitters especially get a bit nervous about substituting a yarn.  It’s actually not a difficult thing to do but there are a few things that you need to consider…

1. Tension / Gauge

Probably the most important thing for a knitter is understanding tension/gauge – and believe me I never thought I’d say that! Every knitter’s tension is different. The tension indicated in a pattern produces the dimensions for the pattern size that the designer got with the indicated needle size.

To test your tension against the recommended needle size in the pattern you will need to knit a swatch.  This is essential before you start a project – especially a large project.  There is nothing worse than spending all your time (and money) only to find that the fair isle sweater you’ve been working on for months has come out too big or too small. Imagine the pain of having to frog (rip) that one :-O

If your tension measurements show that you have too many stitches per inch then you will need to go up a needle size while if you have too little then you needle to go down a needle size.  Your individual tension will affect the amount of yarn you use.  So it is important to follow the pattern tension to ensure you have enough.

But how do you measure your tension?

The tension indicated in a pattern could say for example 28 sts by 28 rows over 4 inches. So this means you will need to have 7 stitches across per inch and 7 rows per inch.  You’ll need to knit a square – pattern usually says in stocking stitch – and then lay this flat and use a ruler to measure if your tension is correct.

Remember to make your swatch big enough – its not always enough just to cast on the amount of stitches for 4 inches and then measure the swatch to see if its this size – yarn stretches.  Its also important to wash and block your yarn before you make a final call about tension.  This will give you a full idea as to how the yarn will perform once you have finished your project.

A basic ruler does the job when measuring your tension but you can buy some specialy made tension rulers for knitting.  Tangled Yarn sell both a small and large gauge checkers which I think are very cute.  Churchmouse Yarns & Teas sell a tension ruler that also doubles up as a needle sizer.

2. Yarn Weight

If the pattern doesn’t tell you the yarn weight you can usually work this out from the indicated needle size. For example if it says 5mm it is most likely that an Aran or Worsted weight yarn is appropriate. If you are a member of ravelry you can search the yarn database for the pattern yarn and then you can see details about the yarn like it’s weight, gauge, needle size and fibre type.


The Craft Yarn Council has published the following standards for yarn. You can view this document on their website here


3. Yarn Fibre

Yarn comes from many different fibres these days. Back in the seventies and eighties when knitting was going through a revival your yarn was just called ‘wool’ and you bought it in the ‘wool shop’. However, wool is a generalised term for the yarn that comes from a sheep and there are many different breeds including Merino, Blue-Faced Leicester and Shetland. These days there are much greater options for knitting yarns such as Alpaca, Angora, Cotton, Silk, Mohair, Bamboo and Linen. In fact you can even get Chiengora which is a yarn spun from dog hair!

When you substitute your yarn you may need to consider the fibre that the pattern yarn was made from. Sometimes it is best to use a particular type of fibre for a project – for example if you are making a shawl you will want a good drape and perhaps a blend with some silk would be good, versus if you wanted to make a sweater perhaps a cotton yarn might not be a good idea as cotton stretches a lot with wear (unless you plan to knit a very slouchy sweater).

4. Yardage

Every yarn has a ball band with some essential information on it including the yards/metres for a ball/skein of yarn. It is just not enough to match the yarn by the number of grams as every 50g ball will have different yardage. A simple mathematical calculation (yes there’s lots of math in knitting) can help you work out how many balls of the substitute yarn you will need. An example has been shown below.


So the pattern suggests that you use Hedgehog Fibres Sock yarn but you have some Debbie Bliss Rialto 4-ply weight in your stash.  The pattern says two skeins i.e. 200grams.  Its not just straight forward enough to have 200 grams of the substitute yarn.  You need to work out the different yardage as follows:

PATTERN:         200 grams = 383 yards X 2 = 766 yards total
SUBSTITUTE:   766 divide by 198 (yards per ball) = 3.86 balls needed

Okay so maybe this wasn’t such a good example because the answer came out that you need same amount in grams i.e. 200gs of the substitute yarn.  But that is down to the yardage per 50 grams being similar.  If the yardage of the substitute yarn wasn’t as generous for example lets say it was 150 yards per 50 grams then this calculation (766 / 150) would have worked out as 5.10 balls.

So what’s your experience with substituting yarns? Have you had problems or perhaps you’ve come up with a different method?

I’d love to hear your thoughts. You can leave a comment below.

Copyright: All images and text are copyright of Gillian Harkness unless otherwise stated. Please ask if you want to use them first.


  1. I barely ever used the called for yarn in a pattern! And I got through pretty much the same process when I substitute 🙂

    1. I’m 50-50 on that score (and that’s probably why I have such a big stash lol) I nearly always want the yarn in the pattern 😀

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