Yarn calculator
Enter how much yarn your project needs and the length on each ball, or switch to substitution: the pattern’s yarn and the yarn you want to use instead. Lengths are matched, not weights, because yarns of the same weight can differ a lot in length.
Your project
Your yarn
About the yarn calculator
Enter how much yarn your project needs and the length on each ball, or switch to substitution: the pattern’s yarn and the yarn you want to use instead. Lengths are matched, not weights, because yarns of the same weight can differ a lot in length.
Part of SmartCalcy’s crafts & sewing tools. It runs in your browser with no account, uses your own currency and units (change them at the top of the page), and gives estimates for information only, so check official guidance before you rely on a result.
How to use the yarn calculator
What it calculates and when to use it
Works out how many balls or skeins of yarn to buy from the length your project needs, or how many of a substitute yarn replace the yarn in a pattern.
How to use it, step by step
- Enter the yarn length needed, or switch to substitution and enter the pattern’s balls and length per ball.
- Enter the length on each ball of your yarn.
- Add an extra allowance and the price per ball.
- Read the balls to buy.
What each input means
- Yarn needed – Starts at 1,100 m.
- Length per ball – Starts at 200 m.
- Extra – Starts at 10%.
How to read the results
- Balls to buy – Whole balls with the total length and cost.
- Left over – Length remaining after the project and allowance.
The formula
Balls = needed × (1 + extra) ÷ length per ball, rounded up. Substitution uses pattern balls × pattern ball length as the length needed.
A worked example
With the starting entries: 1,100 m × 1.1 = 1,210 m; 1,210 ÷ 200 = 6.05, so buy 7 balls.
Assumptions and limits
- Yarns are matched by length, not weight.
- A substitute yarn should also match the gauge.
Common mistakes
- Substituting by weight in grams: yarns of the same weight can differ a lot in length.
- Buying from different dye lots.
Frequently asked questions
How do I substitute yarn?
Match the total length and the gauge, not the number of balls or the weight.
How much extra should I buy?
10% covers swatching and small differences in tension.
Related tools
- Needed
- 1,100 m
- With extra
- 1,210 m
- Left over
- 190 m