As a rule of thumb, your helmet should sit tight, without causing pressure points. If your helmet is too large it can slip during a fall. To make sure that doesn't happen, allow us to help you find the optimal size. You may also want to factor in , if you are going to wear a skull cap or beanie under your helmet? Then allow for more room in the helmet.
Helmet sizes are given in XS, S, M, L, and XL, as determined by the head circumference (in cm). Measure your head circumference just above the eyebrows with a tape measure and note down the measurement. As every brand has a slightly different fit, it's important to check each respective size chart.