Thursday, January 28, 2010

Estimating Yarn Requirements

I got a great question in the comments. If Kathryn knits to match a sewing pattern, how can she estimate the necessary yarn amount?

When I had my yarn shop, we tried to sell people plenty so they didn't run out of the dye lot. Running out of the dye lot creates a terrible situation for the knitter, so we avoided that and cheerfully refunded any extra unopened yarn knitters returned. I tried to get people to buy whatever the written pattern called for plus one ball. We knew that ball was coming back and going into clearance, but the knitter wouldn't be stuck without yarn to finish the project. In eight years I only remember one knitter coming back unhappy because she ran out of yarn.

There was a lady who came around every few months with a list of yarns and dye lots she needed. She had a business service locating the yarn knitters needed to finish projects. It was amazing that she found the matching yarn as often as she did. Just think how many brands, lines, colors and dye lots of yarn there are!

My staff and I also learned that there's tremendous variation in yarn requirements. Cotton seems to weigh the most per yard. You don't get as many yards in a certain weight ball or cone, and you will need more. Thickness matters, too. If the yarn is thick, it will take more ounces for the sweater. If the yarn is thin, it goes father.

I developed some rules of thumb about how much yarn certain projects take. A long sleeved women's medium sweater, pullover or cardigan, takes less than a pound of yarn. The whole sweater takes about 4 times what the back takes, if it has long sleeves. Add yarn for big cowl or shawl collars, belts, or other details. Add for fair isle...add for cables...

Another favorite rule of thumb: 3 pounds of yarn for a nice sized crocheted afghan! I think an afghan should be at least 45" wide and 72" long. Remember, crocheting takes more yarn than knitting for an item the same size. Oh, and get 50 grams (1-3/4 ounces) for one knitted adult sock.

When I got DAK (Design A Knit software for machine knitting), I learned to use the yardage calculator in DAK. You can do your own yarn calculations, though. Multiply the average inches in width by the inches of length, and you've got a rough idea how many square inches in the garment piece. Ignore neck cutouts or sleeve cap shaping and measure it as if it were the bigger rectangles, and that gives you a margin of error so you don't run out.

Next, knit a sample in the same yarn and the same pattern stitch. Weigh and measure your sample, and jot down the square inches (length times width) and weight. The sample's square inches divided by the sample's weight gives you the square inches per ounce (or gram, your choice. I like grams).

When I had my shop and we had to estimate needlepoint wool, we had a big piece of clear plastic marked in square inches. We'd lay it on top of the project and count squares to get an idea how much yarn was needed in the different colors. This would be a good tool to have on hand for knitting, as well.

You do need to weigh accurately. Lately, I've been using a Weight Watchers diet scale for weighing yarn, samples, and garments. At my shop, we had a produce scale just for yarn. I have used a postage meter, too, to do the weighing. I have walked into the grocery store with a bag of yarn before and put it on a scale! They probably think I'm a nut, but at least I don't look dangerous!

Finally, you divide the total square inches in the garment by the square inches per ounce, and you've got a yarn estimate!

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