Head Girth

How do I measure head girth. Since my head is at a angle it seems that that would increase the measurement.

Best done with a fabric measuring tape at full erection. These tapes are sold even at my local supermarket in the household items section - sewing, candles, all that stuff. Measure both around the corona (head rim) and across the head as you look down on it. Jot down what you get and compare in a couple months after your regular PE program.