Making a Gauge Swatch
Source: Martha Stewart Living, November 1997
The first step of any knitting project is to knit a gauge swatch to ensure that the dimensions of your finished project will be correct. A gauge is the number of stitches to be worked over 1 inch of knitting using a particular stitch, weight of yarn, and needle size. The gauge for our basic scarf project is 4 stitches to 1 inch, knitted in stockinette stitch (alternating knit and purl rows), with Aran-weight yarn on size-9 needles.
Follow our basic knitting instructions to knit a swatch at least 6 by 6 inches. To determine the number of stitches you need to cast on for 6 inches of knitting length, multiply the number of stitches in 1 inch of knitting (specified by your instructions) by 6. So, for our basic scarf project, which specifies 4 stitches per inch, you will need to cast on 24 stitches. Knit until your swatch is 6 inches square. Bind off loosely, and lay the swatch flat.
Check your gauge by measuring the swatch; since the stitches at the edges tend to curl inward, or become misshapen, measure just the inner 4 inches of the swatch. Place a tape measure parallel to a row of stitches, and count how many stitches (how many Vs) fall within these inner 4 inches, including half stitches. Divide this number by 4, and compare it with the specified gauge (4 stitches to 1 inch). If there are fewer than 4 stitches per inch, your knitting is too loose; use needles a size smaller. If there are more than 4 stitches per inch, you are knitting too tightly; use needles a size larger.