Even pressure all round with no single point standing out, the skin of the cheeks moving with the shell, and — with the strap done up — it should not roll forward off your head when you try to push it off.
The twenty-minute test
Put it on, fasten the strap, and leave it on indoors before removing any tags. Pressure that is noticeable at minute one and painful at minute fifteen is the wrong internal shape, not a helmet that needs breaking in. The lining compresses slightly with use; the shell and the layer beneath it do not change at all.
The roll-off test, which catches a helmet too large
Strap done up, take hold of the helmet at the back and try to roll it forward off your head. If it comes off, or nearly does, it is too big however the circumference measured.
What “snug” actually means
The cheek pads should press enough that the skin of the cheeks moves when you move the helmet, and you should not be able to slide a finger easily between the crown pad and your head. A helmet that feels comfortable in the shop the way a hat does is usually a size too large.
Where pressure tells you the shape is wrong
Forehead and back of the skull, with slack at the sides, means the helmet is rounder than your head. Pressure at the sides with room front and back means the opposite. Even pressure means it matches, and that is the thing no specification publishes.
What can still be adjusted
Cheek pads in published thicknesses, and on many models the crown pad. A helmet correct at the skull but loose at the cheeks is fixed with thicker pads for a fraction of another helmet — check what a maker catalogues for that model before rejecting it.
Where this page and the manufacturer’s own paperwork say different things, the paperwork wins. Every weight, shell size, armour level, approval version, viscosity grade, chain pitch, pad reference and torque figure on this page comes from the maker’s own published figures, with the unit as printed and the source named. None of it is measured here, and no figure is converted into another convention, because a converted number is a different number. And the limit this page does not cross: a published size is a measurement, never a fit. A head circumference is comparable between brands; the internal shape of a shell is not published by most makers and is what decides whether a helmet is bearable after an hour. This page reports the measurement and says where the measurement stops being enough, and it recommends no size to anybody.
Questions riders send in about this
Should it leave marks on my forehead?
A faint even mark after a long ride is common. A distinct mark in one place is a pressure point, and pressure points do not go away.
How much will it loosen with use?
The lining compresses a little over the first hours. Plan for a small change, not a size.
Last reviewed 18 September 2026