On a lot of my recent patterns, I've included a wee little chart like this.  The shaded column on the left is gauge (in stitches per inch).  The shaded row on the top lists the various sizes the pattern is written in.  The cells in the middle tell you what size finished object you'll get if you make a given size at a given gauge.  So with this chart, if you were working at a gauge of 4.5 stitches per inch, and you make the size medium, you'll get a hat with a finished size of 20 inches. This demonstrates [...]