SkeinMath

Blanket yarn calculator

Weigh a swatch made with your yarn and stitch, enter the size of your blanket, and see how many skeins to buy.

Units for sizes
11 skeins
to buy for the blanket
Yarn
1,056 g
Length
2,112 yd or m
Includes
10% extra

The blanket is 80 times the area of the swatch: 80 × 12 g = 960 g, plus 10% = 1,056 g.

How to use it

  1. Make a swatch with the yarn, hook or needles and stitch pattern you will use for the blanket.
  2. Measure its width and length, and weigh it on a kitchen scale in grams.
  3. Enter the size of the blanket you want, and the weight of one skein from the yarn label.
  4. Optionally, add the skein's length from the label to see the total length of yarn.

How the math works

Yarn use grows with area. A 6 × 6 inch swatch covers 36 square inches; a 48 × 60 inch blanket covers 2,880, which is 80 times as much. If the swatch weighs 12 g, the blanket needs about 80 × 12 = 960 g. With 10% extra that is 1,056 g, and with 100 g skeins you need 11 of them: 10 skeins would leave you 56 g short.

If you entered the skein length, the calculator converts grams to length with the label's own ratio. A 100 g skein of 200 yards gives 2 yards per gram, so 1,056 g is 2,112 yards.

Tips for an accurate result

  • Wash and block the swatch the way you will treat the blanket before you measure it.
  • Include any border in the blanket size, or add more extra if the border uses a lot of yarn.
  • If you can, buy all the skeins at once from the same dye lot, so the color matches across the blanket.

Questions

Why weigh a swatch instead of using a yardage table?

How much yarn a blanket takes depends on your yarn, your stitch pattern and your tension. A swatch made with your own yarn and stitch already includes all three, so scaling it up is more reliable than a general table.

How big should my swatch be?

Bigger is better. Many kitchen scales show whole grams only, so on a swatch of a few grams a 1 g error is a large share of the total. A bigger swatch keeps that error small.

Does it work for crochet and knitting?

Yes. The method only uses the swatch size and weight, so it works for any stitch, knit or crochet.

Why add extra yarn?

Borders, seams, joining squares and weaving in ends use yarn that a plain swatch does not show, and dye lots can differ between batches. The 10% is our default; set it to 0 if you prefer to add your own margin.

Related

Published October 13, 2026.