Helmet sizes by head circumference

Wrap a soft tape around the widest part of your head, about 2 cm above the eyebrows and ears, read the number in centimeters, and find it in the chart. Bike, ski and motorcycle helmets all go by that one measurement, though each model sets its own ranges.

The chart is copied from Ruban Size's Helmets template, typical values that each store replaces with the ranges of its own helmets, with inches added (2.54 cm to the inch). The maker's chart for a given helmet wins.

Helmet size chart

Size	Head (cm)	Head (in)
XS	53-54	20.9-21.3
S	55-56	21.7-22.0
M	57-58	22.4-22.8
L	59-60	23.2-23.6
XL	61-62	24.0-24.4
XXL	63-64	24.8-25.2

The sizes step by 2 cm of head circumference, from 53 to 64 cm in all.

How to measure your head for a helmet

Use a soft tape, or a string marked where it overlaps and measured flat.
Place it around the widest part of the head: across the forehead about 2 cm above the eyebrows, about 2 cm above the ears, and around the fullest part of the back of the head. That is the template's step.
Keep it level and snug, flat on the skin and hair without pressing.
Measure two or three times and keep the largest reading.

A helmet is measured a little higher than a hat, at the widest part of the head. The full method, with the mistakes that make a head read small, is in how to measure your head for a hat or a helmet.

How to read the chart

The ranges are written in whole centimeters, so there is a gap between each size and the next: XS ends at 54, S starts at 55. A head of 54.5 cm sits between the two. The template's rule for that case: "Between two sizes? Take the larger one and adjust it with the pads." A helmet a little roomy can be taken in with the pads or the dial; one too small can't be let out.

Outside the chart, there is no size to choose. A head under 53 cm needs a smaller model or a children's helmet; a head over 64 cm a model that goes further.

How a helmet should fit

Once it is on, the template's fit check:

Snug all around, without pressure points.
It stays in place when you shake your head.
It sits level, neither tipped back nor down over the eyes.

Ruban Size's Find my size ends its helmet answers with the same check: "A helmet sits snug and level, and does not move when you shake your head. Adjust it with the pads or the dial." A helmet that moves when you shake your head, with the pads and the dial set, is too big.

Helmet sizes are not hat sizes

Both go by head circumference, but the ranges differ. In Ruban Size's templates, a 56 cm head is a hat M (56 to 57 cm) and a helmet S (55 to 56 cm); a 57 cm head is an M in both. Always read the helmet's own chart. Hat sizes, US hat numbers included, are in hat sizes: head circumference to US hat size.

Children's helmets

The helmet template starts at 53 cm. Ruban Size's Kids' hats template shows how far below that children's heads run: 40 to 43 cm at 0 to 6 months, 50 to 51 cm at 2 to 4 years, 54 to 55 cm at 8 to 12 years. A store that sells children's helmets needs a chart of its own, by head circumference, not by age.

How a Shopify store should show helmet sizes

The head circumference of each size, in centimeters with a switch to inches, per model: two helmets of one brand can have different ranges.
Where to measure: about 2 cm above the eyebrows and ears.
The rule between two sizes: the larger one, with the pads or the dial.
The fit check: snug, level, no movement when you shake your head.
One chart per model or range, each on its own products.

How Ruban Size does it

The Helmets template has six sizes, XS to XXL, the head circumference in centimeters, a How to measure step linked to the head measurement on the figure, and the note quoted above. It opens as a draft and shows nowhere until you save it and choose its products. Shoppers switch between cm and in with one tap, inches first in the US.

Find my size for helmets asks for one field, Head. There is no Snug, Regular or Loose choice for a helmet. In the chart's Fit tab, "Between two sizes, suggest the larger one" is on by default for helmets. A head of 58.4 cm, between M (57 to 58) and L (59 to 60), gets "You are between M and L. We suggest L." with "Between two sizes, we suggest the larger one." A head of 57.5 cm gets "Your size: M".

Find my size never pushes past the chart. A 64.5 cm head gets "Your measurements are above our largest size (XXL). Check the unit (cm or in), or contact us." And a shopper who types 57 in an inch field reads "These look like centimeters, and the fields are in inches."

When helmets of different models have different ranges, give each model its chart and match them with the display rules, by product, tag or collection. A product that matches several charts shows them as tabs.

The real size guide: Helmet size chart. Switch units, or open Find my size.

Size	Head (cm)
XS	53-54
S	55-56
M	57-58
L	59-60
XL	61-62
XXL	63-64

How to measure

Head: around the widest part of your head, about 2 cm above the eyebrows and ears.

A helmet should feel snug all around, without pressure points, and stay in place when you shake your head. Between two sizes? Take the larger one and adjust it with the pads.

Questions

What size helmet do I need for a 58 cm head?

An M in Ruban Size's Helmets template, which covers 57 to 58 cm. A little over 58, between M and L, take the L and adjust it with the pads.

How do I know if my helmet is too big?

It moves when you shake your head, even with the pads and the dial set. A helmet that fits is snug all around, without pressure points, and sits level.

Is my helmet size the same as my hat size?

Not always. Both go by head circumference, but the ranges differ: in Ruban Size's templates, a 56 cm head is a hat M and a helmet S.

What if I'm between two helmet sizes?

Take the larger one and take in the fit with the pads or the dial. A helmet that is too small can't be let out.