Whenever a garment needs to be a certain size, you have to make a gauge. It needs to be done for every pattern and in a size that is at least 4 inches long and wide. The larger your gauge, the more likely it is that the size of your garment will not take you by surprise later on.

After the knitting part is done, count the rows and stitches and note the inches of fabric you have created. Then you can calculate how many stitches and rows are needed for every part of your work. Done!