Having the correct gauge will ensure that your project comes out to the right size specifications. Even a small variation in the gauge can cause problems in your knitting project. This is especially true when knitting items of clothing, which need to be properly sized. Knowing that your gauge is correct also ensures that you can estimate how much yarn you need to complete your project. There's nothing worse than running out of material before the job is completed.
Testing your gauge can be achieved by knitting a swatch. This is basically a test piece in which you can practice getting your gauge correct before you start your project. Most knitters will need to do about 6 inches on the test swatch for the most accurate results. Once completed, count the number of stitches in the 6-inch area and divide by the number six. This will tell you how many stitches per inch that you are knitting.
There are ways to adjust your gauge if you find that your testing swatch is off. Variations of even one stitch per inch can result in a ruined project. To change your gauge, first try changing your needle and yarn sizes. Adjust smaller or larger according to whether your gauge is too small or too large. Also, knitters can change how tight they knit a certain pattern. Pulling the stitches tighter than normal will result in a smaller gauge, while looser stitches will create a larger gauge.
Continue to experiment with stitch tightness, needle size and yarn size until the desired gauge is achieved. When a change is made, the knitter should knit another test swatch for measurement of gauge. Once you can achieve the desired gauge on a test swatch, then you are ready to start on your project. Keep in mind that yarn varies widely and that a particular size or brand of yarn may not work on every project. Knitters should consider keeping many different styles and sizes of yarn for this reason.