Converting a knitting pattern for different yarn/needle size
12 June 2007
[As requested by sewjenny]
[enormous upfront caveat: this is my way of converting a pattern. It may not work for you. It may not be the 'proper' way to do it. But it's how I do it and it works for me. All care taken, no responsibility accepted]
Sketch out the shape of the pattern piece, fairly large.
Write the number of stitches on the sketch at each point where it changes.
At each point where the number of stitches change, write down how many rows it took to get to that point.
Using the tension given in the pattern, work out how many centimetres wide or high the piece is at each of these points. Write these on the sketch at the appropriate points. Here’s my picture for the grey cardigan
For example, if the tension is 10cm x 10cm = 22 stitches and 31 rows; and the pattern instructions say
cast on 97 stitches,
work 6 rows,
increase by 2 stitches at each end of the next two rows
(8 rows total, 101 stitches)
then (using the conversion 1 stitch = 0.45cm and 1 row = 0.32cm) this instruction in centimetres is:
cast on 44cm
work 0.31cm which is 45cm long
work 0.31cm which is 45.91cm long
Now, knit a tension square in your chosen wool with your chosen needles.
Measure how many stitches and how many rows there are to 10cm.
Now ‘back-calculate’ from your centimetre sketch to your new tension.
For example, if your tension square has 15 stitches and 20 rows to 10 cm, then (using the conversion from your new tension square that 1cm= 1.5 stitches or 2 rows) the measurements above become:
cast on 66 stitches
work 3.75 rows
work 0.62 rows and increase the row length to 67.5 stitches
work 0.62 rows and increase the row length to 68.86 stitches
Write these on the sketch too.
Now, there’s an obvious problem – we need the pattern to have whole numbers of stitches and rows. So let’s look at that set of instructions again. We can start with 66 stitches; though 65 or 67 would probably be better, because an odd number of stitches gives the finished garment a neater centre line. In total we need to work 3.75 + 0.62 + 0.62 rows = 4.99 rows – let’s round this up to 5 rows. We also need to increase by 2.86 stitches – we can round this up to three, but that makes it harder to work them symmetrically. So we can either increase by 2 stitches in our last row, and ‘carry forward’ an increase to the next increase point; or we could increase by 4 stitches and increase by 1 less at the next increase point. If we’d decided to cast on 67 stitches instead of 66, we can increase by 2 and have the right number of stitches. The pattern for the new wool and needles is:
Cast on 67 stitches
Work 4 rows
In row 5, increase by 1 stitch at each end
Do this for the whole pattern piece, always keeping in mind that it needs to fit the measurements in your diagram. It is also worth remembering that it’s easier to increase/decrease in a knit row, rather than a purl. And that your increases and decreases need to happen smoothly, so spread them out evenly.
This method is much easier for simple garments – for one that has lots of shaping or set in sleeves, I would either change your needle size to get as close as possible to the suggested tension; or if that’s too hard and you are trying to get 10-ply wool around 2mm needles, find another pattern. It’s not impossible to do it for complicated shaped patterns, it’s just a lot of work. You pretty much need to set up the above calculations in a spreadsheet to keep track of them. [Nerd alert!] I do have such a spreadsheet and I’m happy to share it [/end nerd alert].