Did you shudder at the sight of the word? Shrink back in fear? I've been knitting for over ten years, and working on a gauge swatch can still fill me with, if not outright terror, at least dread.
Lately, I've been working with a number of contract knitters to produce pieces for my business, and the issue of gauge has arisen. Namely, they weren't able to get the same gauge as I did for a piece, and they didn't know how to adjust for it. Two knitters with whom I'm no longer working didn't even bother to check their gauge, which led to them mailing me pants with a 12-18 mos inseam and a 3-6 mos waist. Oops! A perfect example of why gauge is important.
So - simply put - what is it? Gauge is the number of stitches per inch and rows per inch that your knitting produces. It's affected by how tightly you hold your yarn, how large of needles you're using, or in machine knitting your tension on your carriage and the tension knob. It's a tricky little beast. Typically, a pattern will give you recommended gauge for a 4X4 inch square. Somewhere in the instructions it will say, Gauge = 23 stitches, 34 rows.
All of the instructions in your pattern are based off the math that your gauge gives you. If the size is for a 34" chest knit in the round, the designer will have you cast on 196 stitches* Wait, how did I get that math?
23 stitches/4 inches = 5.75 stitches/inch
5.75 stitches an inch X 34" = 195.5 stitches (rounded it to 196).
Et, voila! So IF you're able to get gauge on your needles for that size, you can cheerfully knit away, following the pattern as you go (though I would recommend measuring occasionally, putting the piece on waste yarn and trying it on at crucial points, etc).
But, um, what if you're me and you knit three different gauge swatches last night and didn't get the correct gauge once? Sigh. Then you have more work to do.
If you're lucky, your pattern will have a chart that indicates what the measurements are supposed to be at key points (the waist, the bust, sleeve length, etc) like this one from KnitScene Summer 2013;
The drawing indicates what measurements should be at the waist, bust, etc. So all you have to do is multiply the measurements by your gauge. For example, if I'm making the smallest size the hips should be 32". In my gauge I got 5.11 stitches/inch instead of what the pattern called for - 5.75 stitches. If I take 32" and multiply it by 5.11 I know that I need cast on 163.52 stitches at the hips.
It's a pain to go through a pattern and re-do all the math, no doubt. Some knitters just chose to wing it, but if you're making a large sweater there's nothing worse than ripping it out and starting all over again. Hopefully this post will help you when you need to make adjustments.
Questions? Ask away in the comments!-Dena *simple example here, I'm assuming no waist shaping/hip width the same