Every craft has tools that are foundational to successfully completing a project. For knitters, these tools are yarn and knitting needles. We operate these tools with our hands, but every knitter's hands are a bit different, and each of us may have slightly different ways of holding our knitting. You may even notice that the way your hands hold your knitting will change a bit if you are very tense or very relaxed, or even sitting in a different way than usual. We also have so many different varieties of yarn and knitting needles available to us, that a thousand different knitters could be knitting the same pattern, each with a different combination of yarn and needles. All of these things may influence the knitted gauge in the finished projects.
Knitting gauge (or 'tension') refers to the number of stitches and rows (or rounds) contained within a particular measurement of the knitted fabric. Most conventional patterns will provide this gauge over 4 inches (10 cm) or 2 inches (5 cm). We encounter this information in pattern notes alongside descriptions of the materials and needles required to knit that pattern. As an example, you might encounter a gauge note referring to "20 sts/ 26 rows over 4 ins on 4.0mm/US6 needles, in stockinette stitch." This note is telling you the gauge as well as the needle size and stitch pattern used. It is typical for patterns to refer to stockinette stitch for gauge, since it is easy to measure. However, more complex patterns using cabled or color-work stitch patterns will tend to offer gauge references over those patterns also.
"There is nothing more important to the fit of any garment you knit than an accurate stitch gauge." - June Hemmons Hiatt, Principles of Knitting
'Getting gauge,' or, executing a knitted item using the same knitting gauge as called for in the pattern, can often require some patience and preparation. Perhaps you are one of those lucky knitters who "always gets gauge," but for the rest of us, knitting a gauge swatch (or 'tension square') is a necessary first step. This is especially crucial before embarking on a large project or a fitted project, like sweaters or shawls. A sweater knitted at a too-loose gauge may turn out to be two or three sizes too big, and a shawl knitted at a too-tight gauge may turn out more like a small scarf. Working a gauge swatch or two before starting on the project will reassure you that you know what kind of fabric your hands will produce. If you are new to the process of gauge swatching, or have been frustrated by this in the past, take heart - you are not alone! Many a knitter has felt these exact same frustrations, and lived to tell the tale.
To make a gauge swatch, you can proceed one of two common ways. The first method is to knit a square with the number of stitches and rows presented in the gauge measurement (from our example above, this would be a square 20 sts wide and 26 rows deep), and to measure the square. If it measures 4 ins wide and deep, then you have achieved pattern gauge. If it does not, then you will need to swatch again using a different needle size. The second method is to knit a large stockinette swatch, 7-8 inches wide and at least 5-6 inches deep, then measure 4 inches across on a portion of the swatch in the middle. If you have achieved the desired number of stitches over 4 ins, then you have "got gauge." If not, you will also need to swatch again using a different needle size. I prefer this method because a large piece of fabric will more closely mimic the way a large garment behaves, in terms of drape, weight, and so on. There is a saying in knitting that "the only true gauge swatch is a completed garment," which means that larger swatches are more likely to be accurate.
Whichever method you choose for working your gauge swatch, do keep in mind one step - always wash and block your finished swatch before measuring the gauge. Many yarns will behave differently after being washed - for example, 100% wool yarn will often 'bloom' after washing, and this results in a slightly looser gauge than when it was freshly knitted. Imagine if this were to happen on a completed sweater - your sweater would grow 1-2 sizes between being knitted and being washed! This would be an unpleasant surprise if you did not expect it to happen. So, it is best to take the time to wash the swatch and allow it to dry, then measure the gauge. Once it is dried, take a moment to note the needle size you used to knit that swatch, and possibly the yarn as well - do this on the swatch itself, or in your notes that you can refer to later.
Swatches will tell you many things about the knitted fabric you will create with your yarn. Along with gauge, you will discover how the yarn feels in your hands and how well you enjoy knitting with it. Swatches are also a good opportunity to practice a stitch pattern that will be used in the full garment, such as cables or lace patterns. Once you have practiced the stitch pattern in swatch form, it will feel much easier and familiar by the time you begin the actual project.
Knitted swatches will also reveal how the fabric behaves. Whether it is very stiff or very light and drapey, is something that will help you understand whether it is right for your project. A very stiff fabric, for example, would be less desirable for a sweater meant to be loose and airy, but useful for mittens and hats that you might like to be more 'wind-proof'. You will also discover the quality of stitch definition in the finished fabric, and how well it shows off your stitch patterns.
Swatches do take time and effort to create, but it is much less time than the full project itself, and it is time that can make the difference between a finished garment that fits and one that does not. You never know what you might learn in the process! What projects are you hoping to swatch for next?