How to measure your head for a hat or a helmet

A hat size is a head circumference. Wrap a soft tape around your head just above your eyebrows and the tops of your ears, around the fullest part of the back of your head, and read the number in centimeters. On the Ruban Size hat template, a 57 cm head is an M, or a US 7⅛.

For a helmet, measure the same way, around the widest part of your head, about 2 cm above the eyebrows and ears. In both cases, if you fall between two sizes, take the larger one.

How to measure your head

1. Use a soft tape measure. No tape? A string or a strip of paper, marked where it overlaps, then measured flat against a ruler.
2. Place it where the hat sits: across your forehead just above the eyebrows, just above the tops of your ears, and around the fullest part of the back of your head.
3. Keep it snug, not tight. It should lie flat on your skin and hair without pressing in.
4. Read where the tape meets its start, in centimeters if your tape has them. Inches times 2.54 gives centimeters.
5. Measure two or three times, moving the tape a little each time, and keep the largest reading.
6. For a helmet, place the tape around the widest part of your head, about 2 cm above your eyebrows and ears, as the helmet template's step says.

Hat sizes from your head measurement

The Ruban Size hat template uses letter sizes, with a row of US hat sizes beside them:

A US hat size is the head's circumference in inches divided by pi (3.14), as if the head were round and you measured across it. A 56 cm head is 22.05 in; divided by 3.14, that's 7.02, a size 7. Every value on the template's US row follows that arithmetic to the nearest eighth. There's a longer table in hat sizes: head circumference to US hat size.

Helmets

Helmets are sized on the same measurement. The helmet template runs from XS to XXL in steps of 2 cm:

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

Kids' hats

Kids' hats are labeled by age, but each age stands for a head measurement, and the measurement is what to check. The kids' hat template:

Its note says it plainly: "Between two sizes? Take the larger one: little heads grow fast." Measure a child the same way as an adult, just above the eyebrows and ears. For the rest of a child's wardrobe, see how to measure kids for clothes.

Common mistakes

• Tape over the ears or too low on the forehead. That isn't where a hat sits, so it isn't the number a hat is sized on.
• Tape too high at the back. It misses the fullest part of the head and reads small.
• Pulling it tight. A hat sized on a squeezed head presses all day.
• Measuring once. A size covers only 2 cm, so a tape that sits a little high or low can change it. Measure a few times and keep the largest.
• Taking the smaller size when between two. For hats and helmets, the larger one is the safe side: helmet pads take up the extra.
• Buying kids' hats by age alone. The age is a shortcut for a head measurement; a quick tape around the head is better.

What it means for a Shopify store

Hats and helmets have one measurement, so the chart can stay short: the sizes, the head circumference in centimeters with a switch to inches, and the US hat size for American shoppers. Add the "between two sizes" advice to the guide, and for helmets, how a helmet should sit.

Three templates cover it: Hats and caps, Helmets and Kids' hats. Each opens as a draft with typical values, and shows nowhere until you save it and choose its products. Here is the hat template as shoppers see it:

How Ruban Size handles hats and helmets

On a hat or helmet chart, Find my size asks for one field: Head. When the head falls between two printed ranges, the larger size wins. A 57.2 cm head sits between M (56 to 57) and L (58 to 59), and the answer reads "You are between M and L. We suggest L.", with the line "Between two sizes, we suggest the larger one." In the chart's Fit tab, "Between two sizes, suggest the larger one" is on by default for hats and helmets, and can be turned off.

Hats offer "Fit I like: Snug, Regular, Loose". Snug moves the target a quarter of a centimeter down, so the same 57.2 cm head gets an M, at the top of its range, for someone who likes a hat that grips.

Helmets get no fit choice: a helmet fits one way. A 58.3 cm head on the helmet template sits between M and L and gets L, and every helmet answer ends with "A helmet sits snug and level, and does not move when you shake your head. Adjust it with the pads or the dial."

On both, the guide shows inches as fractions (22½, not 22.5), and Find my size spots centimeters typed into inch fields. These rules are part of fit by product type, next to rings, shoes, gloves and belts, and they load only on the charts that need them. More on units in centimeters to inches for size charts.

Questions

Where do you measure your head for a hat?

Just above your eyebrows and the tops of your ears, around the fullest part of the back of your head. For a helmet, around the widest part, about 2 cm above the eyebrows and ears.

What hat size is a 57 cm head?

On the Ruban Size hat template, 57 cm is an M, a US 7⅛. Brands differ, so check the chart of the hat you're buying.

Should I size up or down between two hat sizes?

Up. The hat and helmet templates both say to take the larger size, and Find my size suggests the larger one when a head falls between two ranges.

How do I convert head circumference to a US hat size?

Divide the circumference in inches by 3.14. A 58 cm head is 22.83 in, and 22.83 divided by 3.14 is 7.27, a US 7¼.