“Your tape measure, or string, should rest where the brim of your hat would sit,” Carmona says. This is usually the widest part of the head. The measurer should run straight around your head (parallel ...

Hey Ray: Using Pi to measure hat size 02:12. There is Pi all around us, in ways you may not have seen before. If you remember from school, Pi is the ratio of a circle's circumference to its diameter.