Fit, sizing and safety ratings

Wrap a soft tape measure around your head just above the eyebrows and the tops of the ears, at the widest point. Measure two or three times and keep the largest number. The helmet size finder turns it into a size range; each brand's own chart has the final word.

Heads come in roughly three shapes seen from above: long oval, intermediate oval and round oval. A helmet made for a different shape presses on the forehead or the sides even when the size is right. A good fit is snug on the cheeks, has no pressure points after 20 to 30 minutes, and does not roll off when you pull up at the back with the strap fastened.

DOT FMVSS 218 is the US federal standard: the maker self-certifies and NHTSA buys and tests helmets to check compliance. ECE 22.06 is the UN regulation used in Europe and many other countries, with lab type approval, batch testing and an oblique impact test. Snell M2020 is a voluntary standard from a private foundation. A label means the model met that test when it was made; the rating decoder explains each one.

Ready when: You have your head circumference in centimeters, you know your head shape, and the helmet you want carries a DOT label for street use.