Gauge, or tension, is the fine art of making sure you get the same number of stitches and rows per inch as the designer did. If she got four double crochets to the inch and you are getting three or five (or two or seven), you are going to have some serious sizing issues. And size matters. Even for a scarf, you don’t want something to turn out to be 3 inches wide if you had intended it to be 6 inches, or 18 inches wide, either, for that matter. Don’t ask me how I know, let’s just say I have some personal experience with the “you don’t need to worry about gauge on scarves” school of thought. My personal experience is two feet wide and nine feet long, and despite the fact that I am a tall person, when I wear this scarf—and I do—I need to arrange it artfully lest I look like I am being devoured by blue merino.
If you are getting more stitches and rows to the inch than you should, you need to go up in hook size until you get where you need to be. If you are getting less stitches or rows to the inch, you need to go down a hook size or more. Or sometimes, it’s the yarn substitution you made that is throwing you—you might need a thicker or thinner yarn to obtain the right gauge. Or the needle material—metal is slipperier than bamboo and switching from one to the other can change your gauge. Or if you are happy with your crocheted fabric, you can redo all the math in the pattern to make it work out for the gauge you are happy with, or go up or down a size from what you would normally make to accommodate the difference. Or you could do one of these two things:
For tight crocheters: Just add water. Fermented water, that is—a glass of wine or three or a couple of beers is bound to loosen up a too-tight gauge. Just make sure you knock back a few each time you want to crochet or your gauge will be inconsistent throughout the project. This technique might interfere with an accurate stitch count, but hey, we are talking about gauge here.
For loose crocheters: Watch the evening news, call your least favorite relative, or do your income taxes. All of these are likely to make you at least a little tense, and you will tighten up a loosey-goosey gauge in no time. Alternate these activities with other guaranteed stress producers throughout and not only will your gauge be right on, you will be so happy to sit down and crochet instead of doing anything else that you will get a lot of crocheting done in no time.
See? Gauge is important, but there are many techniques available to you to help you achieve your goals.
Oh and I forgot one more—check for pattern errata. There may have been a misprint in the stated gauge, yarn weight, or hook size. Oops…