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 1.875cm
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].


6 Responses to “Converting a knitting pattern for different yarn/needle size”

  1. Tanya said

    You have explained this very well, I think if someone didn’t know how to do it they would be able to follow your instructions easily and work it out. I would love to see your spreadsheet, are you able to email it to me? It is so interesting (to me, a fellow nerd!) how other knitters work this stuff out. It is funny even after knitting for a while how much you can learn from fellow knitters, even small stuff. For example I don’t properly draw the garment to make changes, I photocopy the pattern and then mark all over that but I like your approach better. It seems like you basically rewrite the pattern and knit it from a chart (like in Japanese knitting books). Much better plan, now why didn’t I think of that – duh! Thanks for the pointers. (Now back to that sweater that I am dying to rip off from Country Road……..)

  2. sewjenny said

    Dear Ali
    thank you so much for explaining this. I’m a humanities nerd despite doing sciences to VCE level – so numbers are not my strong point. I’ll be printing your ‘how to’ and poring over it until I’ve grasped it (am sure it’ll be as good as sudoku in keeping the brain fuzzing nasties away!!!). I’d love to see the spreadsheet too, if you could send it.
    You and Tanya might get a big laugh out of this – I did my first tension square last night – am knitting a country silk 8ply cardigan from the next pattern book after the one you converted to 10ply. I’ve always avoided tension squares (too impatient) but have decided to try to become a disciplined knitter… Anyway, I carefully did the square, did the measurements under a lamp in the bathroom (!?!?!) and thought “hmm, you need smaller needles”. When I went lokoing for smaller ones in my mum/grandmas bag of needles that’s been passed on to me, I came to the realisation that I’d knitted my tension square with needles two sizes bigger than the recommended ones – gaaahhhhh! I’m now knitting with the recommended ones (back on track!) but seem to have more stitches than required, so think I need actually go to up a size.

    Thanks for your site, and your work in explaining this to me – I’m looking forward to benig a grown up knitter one day, and shall look forward to reading of your crafting exploits in the meantime.



  3. Sheila said

    I have been trying to figure out how to change my pattern, because the yarn i am using is a different weight. I really am not to good at numbers, but if you know of a way to figure out how to use worsted weight instead of sport weight, please let me know. i am trying to knit a very easy skirt for my grandaughter, and not sure how to do it. the gauge of the pattern is:sport weight yarn, 22 sts and 28 rows=4′ with size 6 needles, the yarn i am using is:worsted weight, and the gauge is:18 sts and 24 rows is 4″,on size 8 needles, the pattern says to cast on 128 sts, so i am trying to figure out how many to start with,(my husband says he thinks it would be around 105 sts) since the skirt is fairly straight, i can probably figure out how to increase..any help would be greatly appreciated…thank you ..sheila

  4. Marie Schlegel said

    I would love to see your spread sheet on changing the pattern.
    I know nothing about how to do this. It would be so helpful to be able to make the same for instance, baby hat from Worsted to a lighter weight yarn….Have to change needles & yarn cast on & etc.

    Thanks for your help…..

  5. Christine said

    My mum used to be able to do these conversions, but unfortunately never passed it to me, thank you so much. Would love to see your spreadsheet

  6. Kerry said

    wow that is quite involved you are clever to be able to do that. I might try it out myself but whether I will succeed is debateable lol. thank you for sharing. kerry

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