Hat Sizing and How to Measure your Head
An average head size for a man is 58 cms in European Sizing or 7 1/8 UK sizing and 7 1/4 US sizing. The average head size for a lady is 55 cms. Probably the largest head size you will ever find, will be 64cms and the smallest 51cms.
Head sizes and shapes differ from country to country with the smallest heads being in the Far Eastern countries and the largest in Germany. With regards to shape, these can be either very round or oval, with the far eastern countries having a rounder head and the western countries tending to have a more oval shape.
How to measure your head
Take a measuring tape and place it around the circumference of the head, slightly above the ears.
Hat Measuring Chart