1. Get a tailor's tape measure and a mirror.

2. Take the tape measure and place it on the nape of your neck; then bring it forward on both sides, passing slightly above the ears, above the eyebrows, and approximately in the center of the forehead. Make sure the tape is not too tight.

3. Read in the mirror the circumference of your head and compare it with the chart above to find your size.

4. Here's a tip: if you don't have a tailor's tape measure available, you can use a ribbon or cord instead and then check the measurement on a rigid tape measure..