How Much Yarn Is Enough? Part 2: Estimate Yarn Requirements by Area

This this two-part series walks you through proven ways to know in advance if your yarn supply is adequate for the project you have in mind. In the first part, you learned how to make rough estimates of yarn requirements by weight and how to make more specific estimates by measuring a sample swatch. In part two, explore Rita's second method: estimating yarn requirements by area. Though this process takes longer, it gives more accurate estimates than a simple comparison of weights.

Estimating Yarn Requirements by Area

Although carrying this method through may take an evening, I think it’s worthwhile insurance for projects that will require several weeks’ knitting. To estimate yarn use by area, you figure the approximate area of your intended project in square inches, measure a sample swatch to determine the number of yards or grams of yarn per square inch of knitting, and multiply to find the total yardage or weight required.[PAYWALL]

It’s easy to figure the area of a project if you’re making something rectangular: just multiply the length times the width. For example, a scarf 10 inches wide by 60 inches long has 600 square inches. It’s a little more trouble to estimate the area of curved and fitted garments, but if you have something similar to what you want to make, you can measure and multiply and total up the requirements for front, back, sleeves, etc., or use the information on the pattern's schematic. To make it easier for folks who fear math, I compiled a chart of approximate areas (in square inches) for common knitted items.

Rita figured out the approximate surface area of several popular project sizes, given here in square inches.

You can figure yarn use per square inch at the same time that you’re knitting sample swatches to confirm your gauge or to test different stitch patterns. The trick is to start with a known amount of yarn, measured by length or by weight.

To work by length, start with 20 yards of yarn. Knit a swatch and block it, measure its length and width, and multiply to find its area in square inches. Divide 20 yards by the area to determine yards per square inch. Multiply this number by the project area to determine length of yarn required.

These four swatches show the same length of yarn—10 yards. Clockwise from top left, merino/silk singles, wool chainette, merino/linen/silk blend, and alpaca. Photo by Matt Graves*

In the samples pictured above, the pink swatch was knitted on size 2½ (3 mm) needles, is 4" x 2", and uses about 1.25 yards per square inch. The light gray swatch was knitted on size 9 (5.5 mm) needles, is 3¾" x 4", and used about .67 of a yard of yarn per square inch. The dark gray swatch was knitted on size 3 (3.25 mm) needles, is 3¼" x 3", and used about 1.03 of a yard of yarn per square inch. The teal swatch was knitted on size 6 (4 mm) needles, is 5" x 3½", and used about .57 yards of yarn per square inch. Measuring by length, thick yarn goes farther than thin.

To estimate by weight, you’ll need a scale or balance that accurately measures fractions of an ounce or grams. I usually start with 10 grams of yarn. Knit a swatch and block it, measure its length and width, and multiply to find its area. Divide 10 grams by the area to determine grams per square inch. Multiply this number by the project area to determine total weight of yarn required.

Now you’ve figured the amount of yarn it would take to knit your intended project. The final questions are, “How much yarn do you have?” and, of course, “Is that enough?”

Again, you can work by weight or by length. To determine how many grams or ounces you have, simply weigh the yarn. Use the best scale you have access to, since a few ounces more or less can mean the difference between a sweater that’s all one color and a sweater with pieced-on collar and cuffs.

To determine how many yards of yarn you have, count the number of turns as you wind it onto niddy-noddy, then multiply by the circumference of the skein after you’ve removed it from the reel and let it relax and draw in. If you have a McMorran balance, use it to determine the yarn’s grist in yards per pound and multiply by the yarn’s weight in pounds to find how many yards you have.

I hope it’s enough and wish you happy knitting.

Rita Buchanan was associate editor of Spin Off in the 1990s. Now retired, she spins more than ever and uses handspun exclusively for her many knitting, weaving, and hooking projects.