To choose the right helmet size online, measure around the widest part of your head with a soft tape, take the largest of three readings, and compare it with the size chart for the exact helmet you're buying. If you land between two sizes, the smaller one is usually right, as long as it doesn't create sharp pressure. Then confirm the fit at home before you ride.
Here's how to get each step right.
Where the tape measure should sit
- Front: about a finger's width above your eyebrows.
- Sides: just above the tops of your ears.
- Back: over the fullest part of the back of your head, not down at your neck.
- Level: keep it horizontal all the way round. A tape that dips at the back gives a wrong number.
- Snug: firm against your head, but not pulled tight into your skin.
Use a soft sewing tape. If you don't have one, wrap a piece of string or a charging cable around your head, mark where it meets, and measure it flat with a ruler.
Measuring on your own
You can do this alone. Stand in front of a mirror so you can see the tape at the front and sides. Hold the zero end on your forehead with one hand and wrap the tape around with the other. Check in the mirror that it's level, then read it. Do it three times and use the largest result. If the readings differ by more than about half a centimeter, do it again more slowly, or ask someone to check the back.
Reading the size chart
- Use the chart for that model. Sizes vary between brands and between models from the same brand. A medium in one helmet can be a large in another.
- Use centimeters if you can. They're more precise than inches.
- Don't use your hat or clothing size. They don't translate.
- Don't use height or weight. Only your head measurement matters.
Why size charts matter more online
In a shop, you can try three sizes in five minutes. Online, the size chart is your try-on. That's why it pays to read it closely rather than glance at the letter. A good chart gives a range in centimeters and inches for each size. If a listing only shows S, M, L and XL with no measurements, ask the seller before ordering.
Also know that many helmets come in only two or three outer shell sizes, with different padding thicknesses inside to cover the full size range. Two sizes that share a shell can feel similar from the outside but quite different inside. The size printed on the label refers to the inside fit, which is what your measurement should match.
Choosing your starting size
If your measurement sits in the middle of a size range, that's your starting size. If it sits at the edge, or the ranges overlap, think about your head shape and how previous helmets felt.
- Previous helmets felt loose or moved: lean toward the smaller size.
- Previous helmets pressed hard on your forehead or temples: the shape may be the problem, not the size.
Between two sizes?
New helmet padding is firm and settles over the first few rides. A helmet that's snug but not painful on day one usually becomes comfortable. A helmet that already feels roomy only gets looser. So the smaller size is often right, unless it creates a sharp pressure point or you can't get it on. More detail in stuck between two helmet sizes.
Why a measurement can still lead to the wrong size
- The tape was too low at the back or tilted.
- You measured once and rounded down.
- Your hair was up, or you measured over a thick cap.
- You used another brand's chart.
- The size is right but the shape isn't. See when the size is right but the fit feels wrong.
Check the fit when it arrives
- Put it on. It should take a little effort. Your cheeks should be pressed gently.
- Check the position. The front edge sits just above your eyebrows.
- Shake test. With the strap fastened, turn the helmet side to side. Your skin should move with it.
- Roll-off check. Try to roll it forward off your head. It shouldn't come off. See the roll-off check.
- Wear test. Keep it on for 20 to 30 minutes indoors. Watch for pressure building on your forehead or temples.
If it feels tight, read how to tell if a helmet is too tight. If it moves, read why a helmet feels loose on the sides.
Ask before you order if you're unsure
If you're between sizes, at the top of a range, or have had fit problems before, contact the seller before ordering. Give them your measurement in centimeters, the size and brand of a helmet that fit you well (or badly), and where previous helmets pressed or moved. That's enough for a useful recommendation and saves an exchange.
Things that change your size
- Long or thick hair: measure the way you'll wear it under the helmet. See long hair and helmet fit.
- Balaclava: if you always wear one, measure with it on.
- Glasses: don't change size, but test with them on.
FAQ
Is helmet size the same across brands?
No. Always use the chart for the exact model.
Should I size up to be safe?
No. A helmet that's too big moves around and is less stable. Choose the size that's snug.
How tight should a new helmet feel?
Snug all over, with your cheeks gently pressed, but no sharp pressure points. See how long a new helmet should feel tight.
Can I measure with a regular ruler?
Use a string or cable around your head first, then measure that against a ruler.
What if I'm right at the top of the largest size?
Look for a model with a larger size range. See choosing a helmet for a large head.
