How to substitute yarn

So you’ve picked your pattern and you’re stuck choosing your yarn. Maybe the pattern suggests Crazy Sexy Wool from WATG or The Wool from WAK but you want to use a more affordable alternative; perhaps the project uses a DK weight yarn but you fancy using worsted or maybe the pattern asks for a wool based fibre but you’d prefer to use a vegan alternative. The tension (number of stitches and rows per 10 cm x 10 cm) varies between yarns and opting for a different yarn than asked for in the pattern can significantly affect how your project will turn out. Here, I’m going to show you how you can alter a pattern if you have a different tension than stated on the pattern and changing needle size can’t seem to sort it out or if you want to use a different yarn.

Please note: I’ve only done this for simple patterns - i.e. stitches which use only variations of knit and purl and projects which are knitted flat and seamed together.

I’ll be using the Seaside Cardigan size large as an example - you can find the pattern for free here.
This pattern uses the John Lewis Super Chunky Yarn (available here) and 12 mm needles. I’m going to adjust the pattern to use Paintbox Yarns Simply Super Chunky (available here)

Step 1 : Make you tension square with your chosen yarn. If you’re using chunky yarn, cast on around 10 stitches; if you’re using a DK weight yarn, cast on 25 stitches. For everything else do something in between. Knit 10 - 20 rows depending on yarn weight and cast off. Measure your square. For the sake of the example, I will use the tension stated on LoveCrafts - 10 cm x 10 cm = 7 stitches x 9 rows.

Step 2: You need to work out how many cm (or inches if your pattern is written in imperial) each stitch and row is.
length / stitch count = stitch cm
10 cm / 7 stitches = 1.4 cm per stitch
length / row count = row cm
10 cm / 9 rows = 1.1 cm per row

Step 3: Adjust the stitch counts in the pattern.
Seaside Cardigan size large - Length - 54 cm, width - 82 cm.
Length of cardigan / height of 1 row
54 / 1.1 = 49 rows
Width of cardigan / width of 1 stitch
82/1.4 = 58.5 stitches - Cast on 59 stitches, knit 49 rows.

Repeat this for all parts of project.

What to do for parts of the pattern where measurements aren’t given
Here, I’m thinking specifically about sleeves.
Calculate the cuff circumference - original yarn tension = 10 cm = 8 stitches
10 cm / 8 stitches = 1.25 cm per stitch
Number of stitches at the cuff - 24
24 stitches * 1.25 cm = 30 cm
30 cm of substituted yarn = 30 cm / 1.4 cm per stitch = 21 stitches
Width of the top of the arm - 45 cm
Number of stitches needed with substituted yarn - 45 cm / 1.4 cm per stitch = 32 stitches
Length of arm - 30 cm
Number of rows required in substituted yarn - 30 cm / 1.1 cm per row = 27 rows
Therefore you need to decrease 11 stitches evenly over 27 rows for the sleeve to be the same as stated in the pattern.

Hope this is at least coherent but if anything is confusing, just get in touch! As I previously said, I’ve never subbed yarn in a complicated pattern nor for a very different weight (i.e DK for super chunky) but this is useful when subbing like for like with a simple pattern.

Abbie xo