Compare lengths first
Multiply the number of pattern skeins by the length of each skein. Add your chosen percentage extra, divide by the replacement skein’s length and round up to whole skeins. Pattern and replacement labels can use meters or yards independently; changing units converts the entered length.
For 5 skeins at 200 m each, the pattern calls for 1,000 m. Replacement skeins of 150 m require 6⅔ skeins, so buy 7. Choosing 10% extra changes the target to 1,100 m and the purchase to 8 skeins. The default extra is zero, so nothing is silently added to the pattern’s allowance.
Matching length does not match the fabric
Yarn weight means thickness, while the grams on a label describe the mass of a ball. Equal weights can contain different lengths. Compare fiber, construction, care needs, stitch definition and drape, then wash and measure a gauge swatch in the project’s stitch pattern.
This is a length-based purchasing estimate, not a test that two yarns are interchangeable. A changed gauge, size, stitch pattern or yarn structure can change actual consumption. The Knitting Guild Association explains both the length calculation and the need to check the resulting fabric.
Colors, held strands and leftovers
Calculate each color separately. For a pattern using two yarns held together, calculate the required length for each strand; do not divide a single-strand requirement between them. If replacing a doubled yarn with one thicker yarn, swatch and establish a suitable length requirement first.
Buy enough from one dye lot. If you have a part-used ball of the same replacement yarn, the yarn length from weight tool can estimate its length separately. This calculator assumes you are buying whole new skeins; it does not subtract stash yarn.
Print or save the plan as a PDF through your browser. My projects saving is optional and preserves all inputs, including the two label units and extra allowance.