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How I Avoid Running Out of Yarn by Using Math

If you feel intimidated by math calculations, stick with me! I promise I will walk you through the calculations so you can also avoid running out of yarn by using math!

When I got close to the end of the Arboreal sweater project that I knit entirely out of handspun yarn, I knew It would be a close call. Would I run out of yarn? I didn’t want to play yarn chicken with my handspun and I had already spun the entire bump of roving, so there was no way to get more yarn for this project.

This is what I did to make sure I could finish my project without running out or having too much yarn leftover.

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Brown handspun yarn in a ball and a handspun sweater sleeve and bottom of the sweater body with knitting needles still attached are placed on a white cloth background with small embroidered flowers. all around
I finished the sleeves first so that I could use the rest of my yarn to make the sweater body as long as possible.

Garment Construction

The first thing I look at when I’m planning my project from the beginning is the garment construction. If I know that I’m making a close call with my yardage, I look for ways that I can ensure I can finish with a wearable garment by adjusting the garment construction and save a few yards here or there if I need to. This helps me avoid running out of yarn. Here are some examples of what I look for:

  • Top down construction – If I run out of yarn, I can make the sweater a crop instead.
  • Sleeves – Will the overall shape and style of the garment work with 3/4 or 1/2 sleeve length? If it does, I can squeeze some yardage out of the sleeves.
  • Stripes and Colorwork – If the garment includes stripes, or colorwork, could another yarn be substituted so I can get all the yardage out of my main color? Could I add a stripe?

The Arboreal sweater had a top down construction. The pattern called for the body to be finished followed by the sleeves. I wanted to make the body of the sweater as long as possible and not end up with one short sleeve, so I knit partially through the body of the sweater, went back to finish the sleeves to length, and then used the rest of the yarn to add to length the body of the sweater.

Know Your Grist

The grist of your yarn is the measurement that compares the weight of the yarn with the length of the yarn, or yards per pound (YPP). If you know your yarn’s grist, you can use that information to make good estimations about how much yardage you have left to work with.

Here is a great article that explains yarn substitutions and grist.

Grist for Consistency

Grist is also important if you want to know how one ball of handspun yarn compares to another ball. For example, during this project I spun some, knit some, and spun some more. I was concerned that my yarn would be inconsistent since time was passing between my spinning sessions. When I calculated my yarn’s grist from one ball of yarn to the next, I was reassured that I was getting the same yards per ounce and that my yarn was consistent. Sure enough, in the final sweater, one ball of yarn transitions to the next within the fabric with no visible differences. Success!

A ball of brown handspun yarn sits on a digital scale
Know your yards and the weight of your yarn to find your grist.

Estimate with Accuracy

I also use a little math trick to figure out how many inches I can knit before I run out of yarn. I have included a helpful graphic below for you to easily plug in your numbers. Here is how I did it with my sweater…

  1. Weigh my working yarn ball (4.4 oz)
  2. Place a removable marker onto a stich
  3. Knit for 2.5″ in pattern
  4. Weigh my remaining yarn (2.5 oz)
  5. Subtract from the original total (4.4oz – 2.5oz = 1.9oz)
  6. Now I know that I used 1.9 oz of yarn to knit 2.5″.
  7. I can do a little math (graphic below) to calculate that I have enough yarn to knit 3.2 more inches of fabric.
  8. Now I know that I can use .6 oz more in stockinette and then switch to the ribbing edge and I will have enough yarn to knit 2″ of rib without running out of yarn!
A pen, calculator and a notebook. The page of the notebook reads Brown, 109 wraps, 4.4 ounces, 230 yards, 1.9 ounces over 2.5 inches equals .6 ounces over 1.3 inches 1.9 ounces equals 2 1/2 inches I have 2.5 ounces left, use .6 more
These are the notes that I used to calculate when I could switch to the ribbing and not run out of yarn.


I know that is a lot of math! I have made a simplified graphic so you can plug in the numbers easily to estimate how much you can knit to avoid running out of yarn. Keep in mind that different stitch patterns will use different amounts of yarn. Ribbing uses a little more than stockinette for instance and so I overestimated the yarn required, just to be safe.

Title Calculate how far you can knit with your remaining yarn 
1. weigh your yarn, total yarn weight 'T' equals 
2. knit in pattern for 2 1/2 inches 
3. Weigh your remaining yarn 'R' equals
4. Subtract the remaining weight from the total yarn weight to find the weight of the yarn used, T minus R equals W
5. Calculate how much more you can knit, 'Y' by entering the numbers from above. 2.5 times R equals X divided by W equals Y inches of knitting remain
6. Now you can knit your project with confidence!

This is the amount of yarn I was left with after my sweater was finished. I felt very comfortable trusting my handspun consistency and my math to know that I would finish my sweater exactly as I expected!

A few yards of brown handspun yarn, a stitchmarker shaped like a mug of cider, and bamboo circular knitting needles on a wooden table.
This is the yarn I had left over. A comfortable amount to finish without playing yarn chicken!

Let me know if you try this formula to finish your knitting project. How did it work? Did you avoid running out of yarn?

Happy spinning and knitting fiber friends!