How do you calculate your head circumference? Nothing could be simpler. Take a tape measure or print out our tape measure and assemble it according to the instructions. Then place the tape measure around your head where the hat would rest (normally between 0.5 and 1 cm above the ears). Do not tighten the tape measure too tightly, otherwise, you risk making a measurement error. Once the measurement is taken, find your size in the table below. If your main size falls in the middle of two sizes, preferably choose the larger one. This will make the hat more comfortable. If, however, you still want to reduce the size, we offer you size reducing cork strips in our accessory section.