Great question! Let's take a look at it and see why it's SO important!
Gauge refers to the number of knitted stitches in one linear inch of fabric. (It also applies to rows per inch, but we'll chat about that another time.) Gauge directly affects the width of your knitted item and, if it's off (even by 1/2 stitch per inch) can completely wreck your project.
Here's an example...
Suppose the pattern you're using states that gauge should be 4 stitches per inch. The pattern also tells you that you need to cast on 60 stitches. When you do the math, that calculates out to a piece o knitting that will measure 15" wide. (Because 60 stitches divided by 4 stitches per inch = 15".)
But what happens if you cast on those same 60 stitches and your gauge measures 4.5 stitches per inch? Now, when you do the math, you see that your finished piece will actually end up being only 13.33" wide. Oops! That's a little small, huh?!
The same thing can happen if you don't have enough stitches per inch. In this case, if you only have 3.5 stitches per inch and your pattern calls for 4 stitches per inch, you'll find that your finished piece will actually end up being 2 inches wider than the pattern says it should be. (Because 60 stitches divided by 3.5 stitches per inch = approximately 17".) Yikes! Now it's going to be too big!
See why it's so important to know what your gauge is before you cast on for that new project?
Next time, we'll chat about knitting a gauge swatch and I'll share some of my favorite tips with you.
Until then, happy knitting!