Like quite a few of you, I’ve been knitting a Carbeth jumper. This one is my fourth, and each iteration has been, in its own way, an experiment. I made the body of number 4 even more cropped than in the pattern (the length from hem to underarm here is just 6.5 inches) and tried knitting, for the first time, with two different shades of Buachaille held together. I used Haar and Squall – two natural shades of grey which unite into a deliciously humbug-y marl.

One obvious question many knitters have, when altering the length of this garment from what the pattern specifies, is how much more (or less) yarn will be required. If you want to knit the body of your Carbeth longer or shorter than the pattern recommends, here’s how to figure that out.

Lets say you are knitting the second size of Carbeth and want to knit the jumper 8 inches longer. To understand how much yarn you’ll need you have to figure out two things:

A: The number of extra stitches you’ll be knitting to reach your desired body length and
B: The weight of yarn (in grams) per stitch.

Contrary to what you might think, neither of these things are difficult to ascertain.

To calculate A (the number of extra stitches required for your added length), you must first work out the total number of extra rounds you need to knit. To do this, simply multiply the pattern’s row gauge by your desired extra length.

In our example, you want to add 8 inches to your Carbeth jumper, so you’ll multiply these 8 inches by 5 rows per inch:
8 inches x 5 rows per inch = 40 rows.

Now you need to multiply the number of extra rows by the number of cast-on body stitches (as the body is worked straight to the underarms we don’t have to worry about shaping). In our second-size example, you’ll have cast on 140 stitches.

140 body stitches x 40 extra rounds = 5600 stitches – so:
5600 = the total number of extra stitches you need to knit to add 8 inches of length to your jumper.

To figure out B (the weight of yarn used per stitch) you need a swatch which has been knitted exactly to the gauge specified in the pattern.

To swatch:
Cast on 50 stitches and knit in the round for 20 rounds. (It’s important to work the swatch in the round because you want it to be knitted in exactly the same way as you will later knit your jumper).
Bind off and block your swatch.
You’ve now worked 1000 stitches, plus the cast on and bind off rows.
Block your swatch. If the swatch is not coming out at the specified pattern gauge (14 stitches and 20 rows to 4 inches), start again, increasing or reducing your needle size accordingly.

Once you’ve got your thousand stitch swatch that is knitted to gauge, weigh it.

My swatch (above) weighs 26g, that’s 1000 stitches, plus two yarn tails, plus the yarn used for the cast on and bind off rows. To exclude the cast on and bind off from the calculation, I’m going to round the weight down to 25g, which is a nice number to work with.

We now know now that 1000 stitches knit to gauge weighs 25g.

And to figure out the weight of a single stitch, we can simply divide the total weight of the swatch by 1000 – so: 25g / 1000 = 0.025g.

a single stitch weighs 0.025g

That’s right: 0.025g! And this scintillating revelation will allow you to calculate how much more yarn you will need.

To arrive at the final weight of extra yarn needed to add 8 inches to your jumper, simply multiply the total number of stitches calculated in part A by the weight per stitch calculated in part B.

In our example, 5600 (extra stitches) x 0.025 (grams per stitch) = 140g

That’s it! You’ll need a extra 140g of yarn to add 8 inches to your jumper. If you are working with Buachaille held double, like me, that’s another 3 x 50g skeins, or if you are working with a standard bulky weight, you’ll need an extra 2 x 100g skeins. If you were being careful, you might also want to add a 10% contingency to your 140g figure to accommodate small gauge differences which may occur when knitting, or disparities in the length & weight of individual skeins of yarn.

I hope this has been helpful and that you (like me) are enjoying knitting this jumper. I’m going to have a go at making a Carbeth cardigan next. Watch this space!

38 thoughts on “how much more yarn will I need?

  1. Thank you for the instructions on adding length. I will use it for the lengthening of the Carbeth. I consider myself a craft knitter (a knitter by the book), and never deviate from pattern or yarn. This will be good for me, if I can do it.

    Liked by 1 person

  2. Kate, you and your designs are killing me. 😄 I don’t have enough hands or time to knit them all. I’m laying aside a very ambitious fair isle sweater in order to start Carbeth. I absolutely
    adore your latest version. It’s this version that forced my hand! Love your designs and the fabulous photos, that make me want to live in your neck of the woods.

    Liked by 2 people

  3. I’m plugging away at my Carbeth, and can’t wait ’til it’s done. I decided to try to make it with a 500-yard skein of yarn that I have had in stash forever, and have been dying to use. However, I think I’m going to want it longer, so I’m planning to find a contrasting yarn to knit the ribbing at the bottom of the body (I used a provisional cast-on for just this contingency); I’ll probably snip the cuffs and knit those to match, too. Stay tuned on whether that works or is a disaster!


  4. Hiya Kate,
    Thanks for showing your design. The style of this jumper is really beautiful and love the tweed choice of yarn. Sorry forgot to say, the ‘Carbeth jumper’. You came up on my Google that’s how I discovered you. Unfortunately, this month is about ‘unfinished symphonies’ that I am determined to complete. Definitely on the list for by resources and pattern. Ssh!

    Thank you so much for sharing. Back to my needle and yarn – sewing together outstanding items only. It’s going to be an exhibition of finished projects at the end of the month.😂.


  5. Thanks so much for this! I always thought that I had to figure out the length I needed, not the weight, because I thought the weight would vary too much with the gauge of yarn. Why did you pick weight instead of length?
    Do you think this would work if calculated by length rather than weight? I’m really curious now!


    1. the problem is, Kay, that commercial skein lengths vary so much from their stated yardage (and are often under or overweight) – so unless you are spinning your own yarn weight is a much more accurate guide. If you knit a swatch to gauge and weigh it, you are there.

      Liked by 1 person

  6. This is so interesting. I’m really tall so always have to make things longer. I generally buy much more yarn that I need just to make sure that I don’t run out. But this sounds far more accurate! Thank you.


  7. Seeing the photos makes me want to have the sweater be much longer simply since it looks as cold where you are as where I am near Woodstock NY in the US. My body is feeling sympathy with the body in the photos and hoping it’s warm enough!


  8. What are the birds in the last photo? Not familiar with birds of Scotland. Have my yarn for the Carbeth. Can’t wait to start….but….if you design a cardi….will I want to knit that??? Kate, you give us so many beautiful choices


  9. I have been meaning to comment on your yarn, the colors are quite wonderful and just looking at the photos makes me want to touch them all.


  10. The fourth one is a keeper. Looks fabulous on you, and love the colour coordinated photo of the feathered friends at the end.

    Looking forward to seeing the cardie. No pressure…!


  11. Kate, that is even nicer on you than the original version, just wish I had the figure to wear it! (But I could knit it for knitworthy members of my family). A beautiful pattern that is really lovely in that combination of colours. And you have snow …..


  12. You make arithmetic fun! The weight of a single stitch – a new way of thinking about stitches (for me at least). Scotland has snow? I didn’t know, although, yes, some of your blog photos show snow on high mountains in the backgrounds sometimes. We just had about 10 inches at my house last Saturday (it drifts so it is hard to tell)

    Liked by 1 person

  13. Would love to knit this jumper but have a busy so a short jumper looks even shorter so thanks for the figures for making it longer -Would 8 inches make the difference? Anyone else info? Also just about to knit the hat from the highland way and have no idea what card means or the symbol of 3 lines like a chicken footprint. Apologies if this is not the right forum for the questions. Thanks Barbara

    Liked by 3 people

    1. Hi – cdd = centred double decrease – (slip 2 as if to k2tog, k1, pass 2 slipped sts over) – it was missed from the abbreviations list.
      8 ins was just an example – you’d have to compare the pattern length to the length you’d prefer to knit.

      Liked by 1 person

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