Yarn substitution calculator
Buy 6 skeins of the substitute. The pattern needs 1,000 yd of yarn, and you will have 20 yd left over.
Result
Skeins to buy
Skeins before rounding up
Yarn the pattern needs
yd
Left over
yd
Pattern yarn, length per hundred grams
m
Substitute, length per hundred grams
m
Substitute's length per weight against the pattern yarn
%
Weight of the substitute you buy
g
Weight of the pattern yarn
g
How it works
A pattern asks for a number of skeins of one yarn, and the yarn you want comes in skeins of another length. Count by length, never by skeins: the tool multiplies the pattern's skeins by their length, divides by the length of your skein and rounds up. That answers how many skeins of a different yarn do I need. Each length has its own unit, so it will convert skeins from yards to meters for you when a pattern is written in yards and the label is metric. For substitute yarn yardage with a margin, add an extra. Under more options, the skein weights show how much yarn to buy when substituting by weight and how the two yarns compare in length per hundred grams.
Formula
length needed = skeins in the pattern × length of one pattern skein × (1 + extra). Skeins to buy = length needed ÷ length of one substitute skein, rounded up. Length per hundred grams = skein length ÷ skein weight × 100 g, for each yarn. Yards and meters are converted with 1 yd = 0.9144 m.
Worked example
The calculator opens with this example; the result above is computed from it.
| Input | Value |
|---|---|
| Skeins the pattern calls for | 5 |
| Length of one pattern skein | 200 yd |
| Length of one substitute skein | 170 yd |
| Extra | 0 % |
| Weight of one pattern skein | 100 g |
| Weight of one substitute skein | 100 g |
| Skeins to buy | 6 |
| Skeins before rounding up | 5.88 |
| Yarn the pattern needs | 1,000 yd |
| Left over | 20 yd |
| Pattern yarn, length per hundred grams | 183 m |
| Substitute, length per hundred grams | 155 m |
| Substitute's length per weight against the pattern yarn | 85 % |
| Weight of the substitute you buy | 600 g |
| Weight of the pattern yarn | 500 g |
Common cases
| Case | Starting values | Skeins to buy | Skeins before rounding up | Yarn the pattern needs | Left over | Pattern yarn, length per hundred grams | Substitute, length per hundred grams | Substitute's length per weight against the pattern yarn | Weight of the substitute you buy | Weight of the pattern yarn |
|---|---|---|---|---|---|---|---|---|---|---|
| Sweater in a yarn with shorter skeins | Skeins the pattern calls for 5; Length of one pattern skein 200 yd; Length of one substitute skein 170 yd; Extra 0 %; Weight of one pattern skein 100 g; Weight of one substitute skein 100 g | 6 | 5.88 | 1,000 yd | 20 yd | 183 m | 155 m | 85 % | 600 g | 500 g |
| Blanket in a bulky yarn | Skeins the pattern calls for 8; Length of one pattern skein 100 yd; Length of one substitute skein 85 yd; Extra 0 %; Weight of one pattern skein 100 g; Weight of one substitute skein 100 g | 10 | 9.41 | 800 yd | 50 yd | 91 m | 78 m | 85 % | 1,000 g | 800 g |
| Cardigan, from large skeins to small balls | Skeins the pattern calls for 9; Length of one pattern skein 200 yd; Length of one substitute skein 109 yd; Extra 0 %; Weight of one pattern skein 100 g; Weight of one substitute skein 50 g | 17 | 16.51 | 1,800 yd | 53 yd | 183 m | 199 m | 109 % | 850 g | 900 g |
| Shawl with a tenth extra | Skeins the pattern calls for 2; Length of one pattern skein 437 yd; Length of one substitute skein 137 yd; Extra 10 %; Weight of one pattern skein 100 g; Weight of one substitute skein 50 g | 8 | 7.02 | 961 yd | 135 yd | 400 m | 251 m | 63 % | 400 g | 200 g |
Questions and answers
How many skeins of a different yarn do I need?
A pattern that calls for 5 skeins of 200 yd needs 1,000 yd of yarn. In skeins of 170 yd that comes to 5.88, so buy 6. You will have 20 yd left.
How much yarn do I buy when the substitute comes in smaller balls?
The pattern needs 1,800 yd. In balls of 109 yd that is 17 balls, which weigh 850 g together against 900 g of the pattern yarn.
Assumptions and limits
- The amount holds only if you knit or crochet to the pattern's gauge. Swatch with the substitute first.
- Two yarns with a similar length per hundred grams are of similar thickness when the fiber is similar. A large difference means a different fabric and a different amount.
- Without an extra the answer is the bare minimum. One more skein is cheap insurance.
- Buy all the skeins at once: a later dye lot may not match.
The result is an estimate for planning, not professional advice.
Sources
- Vogue Knitting: Substituting yarn (balls times length per ball, divided by the new ball's length; keep to one unit)retrieved 2026-10-13
- Lion Brand, Barbara Breiter: 3 questions to ask yourself when you're substituting yarns (round up, buy one extra)retrieved 2026-10-13
- Love Life Yarn: How to substitute yarn (recalculate yardage, round up, add a tenth or more)retrieved 2026-10-13
- Les Laines Biscotte: Knitting gauge and yarn substitution (worked example in meters)retrieved 2026-10-13
Last updated:
Method in depth: Yarn substitution: length, skeins and weight
Cite this page: Knit Math, “Yarn substitution calculator”, https://knit-math.pages.dev/gauge-and-yarn/yarn-substitution-calculator/ (updated 13 October 2026).
Found a mistake? Email handycalc.sites+knitmath@gmail.com.