Reading the length on the ball band
What counts on a skein is not its weight in grams but its length: how much yarn it holds. Two 100-gram skeins can hold 120 or 300 metres depending on the fibre and the thickness. That is the number, given in metres and often in yards, that you enter here. If your label only gives yards, multiply by 0.9144 to get metres.
The chart behind this page is published in yards, like American patterns; we convert it to metres and round to the nearest metre. The number of skeins is always rounded up: nobody buys a third of a skein.
Why a range and not a figure
An adult hat in medium-weight yarn takes, according to the source, between 137 and 229 metres. The gap is not vagueness on the page’s part: it is real. It comes from head size, the height of the hat, the stitch chosen, a brim or a pompom, and how tightly each person works. A textured stitch, such as ribbing or cables, uses noticeably more yarn than a flat one.
Take the low end for a small project in a simple stitch, the high end for a large project or a worked stitch. When in between, start from the high end: a leftover can be stored, a shortfall has to be paid for.
Crochet uses more than knitting
At the same yarn weight, a crocheted piece generally takes more yarn than a knitted one. A crochet stitch is made of looped and knotted wraps that hold more length than a knit stockinette stitch, and the fabric comes out thicker. The chart used here does not tell the two techniques apart; if you crochet, aim for the top of the range, even a little above it for a dense stitch such as single crochet.
The stitch matters more than the technique. Spaced double crochets, an openwork stitch or a granny motif take less yarn than a solid fabric. If your pattern gives a length, it always wins over this page.
Buy one more skein, from the same dye lot
One more skein is the best insurance for a project. First because you can run out before the last sleeve or the last border. Then because the shade changes from one dye bath to the next: the lot number is on the label, and two skeins from different lots can leave a visible band in the work. Buy all the yarn at once, with the same lot number, and keep the label.
If you are unsure of the amount, choose a yarn the brand still makes, so you can buy more. For a large project such as an afghan or a sweater, alternate skeins every two rows if the lots differ: the difference in shade then blends into the fabric.
What if yarn weight means nothing to me?
Categories 0 to 6 in the list are the Craft Yarn Council’s. If you hesitate between "worsted" and "aran", the yarn weight page explains them; to check that your yarn makes the pattern’s tension, the gauge calculator compares the two. The crochet hook and knitting needle pages give the tool that goes with each weight.
Frequently asked questions
How many skeins for an afghan?
For an afghan in medium-weight yarn (category 4), the source gives 1,500 to 2,000 yards, about 1,372 to 1,829 metres. With 200-metre skeins, that is 7 to 10 skeins.
Is this estimate exact?
No, it is a range, and says so. It starts from published charts for adult-sized projects and knows neither your stitch nor your tension.
What if I am a few metres short?
Keep one whole extra skein, from the same lot. For the last border, a partly used skein is often enough, and it stays usable for another project.