The tea cosy has been around since tea began to gain popularity in the 1600s. The tea cosy serves two purposes -- it not only keeps the teapot and the tea inside it warm, it can also be a status symbol, especially if the tea cosy is a fancy one. Protect your own tea pot and give it some class by making your own tea cosy.
Measure around the end of the teapot handle and the tip of the spout with a tape measure. Then measure around the teapot from the top and bottom, making sure you measure around the knob or handle on the pot lid.
Brown paper bags works well for patterns. This paper holds up well, takes repeated erasing, and can be used multiple times. Cut open the paper bag so that it forms one large piece of paper.
Take the measurement of the teapot's circumference and divide that number by two, then add two to that total. For example, if the circumference is 50 cm (20 inches), dividing it by two is 25 cm (10 inches), then add 5 cm (2 inches) to get 30 cm (12 inches). This number is the width of the tea cosy pattern. Repeat the process for the height of the pattern using three instead of two. Use this pattern for the tea cosy's fancy outer layer and lining, as well as any batting you might use as insulation. When you cut the fabric, cut two of each -- two pieces of fabric for the outer layer, two pieces of fabric for the lining, and two pieces of fabric for the batting.