Measuring helmet size sounds like a task for someone who owns a clipboard and says “per protocol” a lot. But it’s actually
quick, cheap, and (best of all) it can save you from the two classic helmet problems: the wobble (too big) and
the headache halo (too small).
Whether you’re shopping for a bike helmet, motorcycle helmet, ski lid, skate bucket, or something sport-specific, the
starting point is the same: your head circumference measured correctly, then matched to the
brand’s size chart. After that, it’s all about fit checksbecause “medium” is not a universal language.
Before You Measure: What Helmet “Size” Really Means
Most helmet sizes are based on one primary number: the circumference around the widest part of your head. That number is
usually shown in centimeters (cm) on size charts (sometimes inches too), and it helps you choose a
starting size.
Here’s the twist: two helmets can both be “57–59 cm” and still feel totally different. Brands use different internal shapes
(round oval, intermediate oval, long oval), padding thickness, and fit systems. So your measurement gets you in the right
neighborhoodthen fit decides the exact house.
How to Measure Helmet Size: 9 Steps
Step 1: Grab the right measuring tool (and a backup)
Use a soft, flexible tape measure (the kind used for sewing). If you don’t have one, use a piece of string, shoelace, or
even a charging cable (yes, really), then measure it against a ruler or standard tape measure afterward.
- Best: Cloth/flexible tape measure
- Works in a pinch: String + ruler
- Nice-to-have: A mirror or a friend to keep the tape level
Step 2: Set your hair the way you’ll actually wear it
Measure with the hairstyle you’ll use under the helmet most often. If you ride with a bun the size of a small planet,
your measurement should reflect that reality. For thick hair, braids, or locs, measure as you normally wear themthen plan
to try the helmet on before committing if possible.
Step 3: Find the correct measurement line on your head
Place the tape around your head about one inch above your eyebrows, running it just above the ears,
and around the widest part of the back of your head (often near the bump at the back). Keep it level
not creeping up toward your hairline like it’s trying to escape.
Step 4: Measure snugno squeezing, no slack
Pull the tape snug enough that it stays put, but not so tight that you’re “measuring” your future headache. The tape should
lie flat against your head, not twisted. Take the number where the tape meets itself.
Step 5: Repeat the measurement 2–3 times and use the largest
Heads are not perfect circles (and tape measures love to drift). Measure at least twicethree times if you’re doing it solo.
If one reading is bigger, go with the largest consistent measurement. It’s easier to snug up a slightly roomy
helmet than to “break in” a helmet that’s clearly too small.
Step 6: Convert units (if needed) and write it down
Most size charts use centimeters. If your number is in inches, convert it:
inches × 2.54 = centimeters. Example: 22.5 inches × 2.54 ≈ 57.15 cm.
Pro move: save the number in your phone as “Helmet size: ___ cm.” Future-you will be grateful.
Step 7: Match your measurement to the brand’s size chart (not a “generic” chart)
Use the helmet brand’s own chart for that specific category (bike, motorcycle, snow, etc.). If you’re right between sizes,
read the brand’s guidance and consider your use case:
- For performance/safety-first fit: many riders prefer the snugger size (if it doesn’t create pressure points)
- For comfort layers: if you’ll wear a balaclava, skull cap, or winter liner, a slightly larger size may make sense
Also remember: some helmets have replaceable cheek pads or liners, which can fine-tune fit after you pick the correct shell size.
Step 8: Try it on and check helmet position (coverage beats vibes)
Put the helmet on level, not tipped back like a backwards baseball cap. The front edge should sit low enough
to protect your forehead without blocking your vision. For many helmets, that’s roughly one to two finger-widths above
your eyebrows.
If your helmet perches high or leaves your forehead feeling exposed, it may be the wrong size or shapeor adjusted incorrectly.
Step 9: Do the fit checks: straps, movement, pressure points, and the “yawn test”
Measurement gets you close. Fit checks confirm you’re actually protected.
- Strap “V” check: Side straps should form a “V” under and slightly in front of each ear.
- Chin strap check: Buckled and snuggenerally only one or two fingers should fit under the strap.
- Movement check: Shake your head “no.” The helmet shouldn’t slide around, rock forward/backward, or rotate easily.
- Pressure point check: Snug all around is good. Sharp hotspots on your forehead or temples are not.
- Yawn test: Open your mouth wide like you’re yawning. The helmet should tug down slightly on your head.
Quick Fit Reality Check: What “Good” Feels Like
A properly fitted helmet often feels slightly tight at first, especially with fresh padding. That’s normal.
What’s not normal: pain, numbness, or a single spot that feels like it’s being bullied.
If the helmet is loose enough to move around when you turn your head, it can shift during impact and reduce protection.
If it’s so tight you can’t wait to remove it, you won’t wear it consistentlyand an unworn helmet protects exactly zero percent of your head.
Special Notes by Helmet Type
Bike helmets
Bike helmets often include a rear retention dial or fit ring that helps fine-tune snugness. Use it to remove wobbledon’t use it
to “force” a helmet that’s clearly too big or too small. After sizing, spend extra time on strap adjustment so the helmet sits
level and stays put.
Motorcycle helmets
Motorcycle helmets usually fit tighter than bike helmets because they need to remain stable at speed and during impact. Cheek pads
can feel firm at first, and a new helmet may “break in” slightly. The key is even pressurenot painful pressure.
Snow/ski helmets
Plan for what you wear underneath: thin beanie, helmet liner, or nothing. Many snow helmets are designed to work with goggles,
so check that the helmet doesn’t push goggles down your nose or leave a big forehead gap (“gaper gap,” if you’ve heard the term).
Skate and multi-sport helmets
These can feel rounder and sit a bit lower for extra coverage. If you’re between sizes, prioritize stable coverage and comfort
you want it to stay in place through repeated movement, not bounce like a soup bowl.
Troubleshooting: Common Sizing Problems (and Fixes)
“I measured correctly, but the helmet still feels wrong.”
This usually means head shape mismatch. Some heads are rounder; others are more oval. If a helmet presses your
forehead but feels loose on the sides, or vice versa, try a different brand/model known for a different internal shape.
“I’m between sizesdo I go up or down?”
Start by considering comfort layers and padding:
- If you’ll wear layers under the helmet, going up can help.
- If the helmet has thick comfort padding that will compress slightly over time, going down can workif there are no pressure points.
- If either size feels wrong, switch models or brands. Your head isn’t the problem. The helmet is.
“It’s tight on my cheeks (motorcycle), but okay elsewhere.”
Cheek pads often loosen a bit with use. But tight should not mean painful, and you should still be able to speak normally.
Many brands offer different cheek pad thicknesses to customize fit after you pick the correct shell size.
“It rocks back when I push it.”
The helmet may be sitting too high, the straps may be too loose, or the size may be too big. Re-check position first (level and low),
then adjust straps, then snug the fit system (if present). If it still rocks easily, size down or try a different model.
When to Re-Measure (Yes, Adults Too)
Re-measure if any of these are true:
- You’re buying a different helmet type (bike vs. motorcycle vs. snow).
- Your hairstyle changed significantly (thick braids, shaved head, extensions, etc.).
- You’re shopping a new brand you’ve never worn.
- You’re buying for a kid or teenhead size can change faster than you can say “growth spurt.”
of Real-World Experiences Measuring Helmet Size
If you’ve never measured your head for a helmet before, the first experience usually falls into one of three categories:
(1) “That was easier than I thought,” (2) “Why is the tape doing parkour on my hair?” or (3) “Wait… my head is how many centimeters?”
All three are normal.
One super common moment is realizing your measurement changes depending on where the tape sits. If it creeps up toward the top of
your forehead, your number can shrinkand suddenly you’re shopping a smaller size that feels fine for 30 seconds and then starts
sending angry emails to your temples. On the flip side, if the tape dips too low in the back (or rides over a bun), the number can
grow and you end up with the dreaded “floating helmet” that shifts every time you check for traffic. That’s why repeating the measurement
is such a big deal: it catches the little errors before they turn into a return label.
Another real-life factor is hair and seasonal gear. People often measure with their hair slicked down at home, then ride with a winter
liner, a cycling cap, or thick curls, and wonder why the helmet suddenly feels like it shrank in the closet overnight. If you know you’ll
wear something under the helmetespecially for snow sports or cold-weather ridingmeasure in a way that reflects that. And if you’re right
on the edge between two sizes, it’s worth trying both rather than betting your comfort on wishful thinking.
Online shopping adds its own “experience pack.” Many buyers nail the circumference but miss the head-shape part. The helmet arrives, and the
size is technically correctyet there’s a single hotspot right in the forehead, like someone installed a tiny thumbtack inside the padding.
That’s usually not you being “picky.” It’s a shape mismatch. Switching to a different model (often within the same brand family) can solve it
instantly. People also discover that two helmets with the same listed size can feel different because one has thicker cheek pads (common in
motorcycle helmets) or a different retention system (common in bike helmets). The measurement is still valuableit narrows the fieldthen the
“try-on reality check” finishes the job.
Finally, the most relatable experience: the mirror test. You put the helmet on, tilt your head, and realize it’s sitting like a tiny hat at
the back of your skull. Nearly everyone does this at least once. The fix is simplewear it level and low enough to protect your foreheadyet
it’s a game-changer for both comfort and safety. The takeaway from all these experiences is the same: measuring is the start, not the finish.
Do the fit checks, trust your comfort, and don’t be afraid to swap sizes or models. Your head deserves better than “close enough.”
Conclusion
Measuring helmet size is simple: use a flexible tape, measure around the widest part of your head (about an inch above the eyebrows and just
above the ears), repeat for accuracy, and match your number to the brand’s chart. Then do the fit checksposition, straps, movement, and comfort
because a helmet that fits right is the helmet you’ll actually wear (and the one most likely to protect you when it counts).