I haven’t knitted in the round for a while and had completely forgotten how to do this so thought it worth posting about.
Most knitters will find that their gauge is different when knitting in the round rather than knitting back and forth. This means that knitting a flat swatch for a project that will be knitted in the round may not give usable results. However, casting on, and then knitting, enough stitches to be able to knit a swatch in the round will take almost as much time as just starting the project and ripping it out if the gauge isn’t right. (Ask me how I know!)
The solution is to knit a swatch half in the round. Cast on, using the needle(s) that you’ll be using for the project, enough stitches for a decent-sized swatch (a 5-inch square swatch should give you sensible results). Knit the first row in the stitch pattern specified by the gauge instructions in your pattern. Instead of turning the work around to work back across the row, as you would when working flat, slide the stitches to the other end of your needle(s) and, loosely stringing the working yarn across the back, knit the next row in the same direction that you knitted the first one. This is similar to the method of knitting i-cord but unlike when making i-cord, it’s very important not to pull the extra yarn tight across the back of the swatch as this will pull the edges of the swatch together and distort it.
Repeat this until you have a swatch that’s large enough for you to measure and calculate your gauge. As with all swatching, this has the potential to save you large amounts of time and energy!