Use a soft measuring tape
Wrap the tape around the widest part of your head
Place the tape about 1 inch above your eyebrows
Keep the tape level all the way around
Measure around the largest point at the back of your head
Pull the tape snug, not tight
Record the measurement in inches or centimeters
Compare the measurement to the helmet brand’s size chart
Try on the helmet to confirm fit
Check that the helmet feels snug all around
Make sure it does not move when you shake your head
Verify that the cheek pads fit firmly without pain
Recheck the size if you are between sizes