Best Bike Helmet for Large Heads: A 60–65 cm Fit Guide

You're not new to this.

You've probably bought two or three helmets already. One didn't close around your head. One closed but perched up there like a salad bowl. One actually fit, but looked like a beach umbrella in the mirror.

Now you're back online, and every article tells you to "measure your head" — like that's the part you haven't figured out.

The problem isn't your measuring tape. It's that the bike helmet industry was built around heads in the 56–60 cm range. Anything above 61 cm has been an afterthought.

This guide skips the basics. It's for the rider who already knows their number is 62, 63, or 64 cm — and just wants to know what's actually going wrong and what to do about it.

Why Most XL Helmets Fail Large Heads

Fit comes down to two things. Most listings only tell you about one.

Circumference — the number on the size chart. The easy part.

Shape — where the trouble starts.

Heads come in three rough categories:

• Round — about as wide as it is long
• Intermediate oval — slightly longer than wide
• Long oval — clearly longer than wide

Most modern helmets are built on an intermediate-oval mold. When manufacturers scale up to XL, they scale it wider, not deeper. The shell gets bigger around. It doesn't get any taller inside.

If you have a tall-crowned head, here's what happens: the XL closes around your circumference but stops short of the bony bump on the back of your skull. That's the "mushroom" — helmet on top, sides of your skull exposed.

Not just cosmetic. That exposed area is unprotected in a crash.

The trend isn't going away

Forensic anthropologists at the University of Tennessee found that American skulls have grown taller and narrower over the last 150 years — skull height up nearly 7%, with the average cranium gaining roughly the volume of a tennis ball.

The helmet industry has been slow to catch up.

"XL" means almost nothing

We've seen helmets labeled XL that top out at 60 cm. We've seen XLs that genuinely reach 65 cm.

Read the centimeter range. Not the size letter.

Measure Your Head (30 Seconds)

1. Wrap a soft tape one inch above your eyebrows
2. Level it across the widest part of the back of your skull
3. Snug, not tight
4. Measure twice — use the larger number

No tape? Use string against a ruler.

Where you land

Shape check (10 seconds)

Take a selfie from directly above, looking down at your crown.

• Roughly circular → round head
• Clearly egg-shaped → oval head
• Circular outline but tall forehead/crown → tall-crown head (the mushroom culprit)

Need more detail? See our full fit guide.

The 6-Point Fit Checklist

Works anywhere you shop. Screenshot it, take it to the bike shop.

Verified max circumference (in cm)

Ignore "XL." Find the cm range. If it says "58–61 cm" and your head is 62 cm — it doesn't fit you. The letter doesn't matter.

Depth of coverage

With the helmet level and dial snug, the bottom rear edge should sit at or below the bony bump on the back of your skull.

Two-finger gap between the bump and the helmet? Too shallow. Mushroom territory.

Retention dial range

Cheap dials only adjust about 2 cm. Borderline fits will max them out and still wobble.

Look for 3–4 cm of meaningful tightening range.

Pad swap-ability

The thick top pads control how deep the shell sits. Swapping thick pads for thin ones drops the helmet 3–5 mm.

That's often the single best fix for tall-crown mushroom.

MIPS at large sizes

On many helmets, adding MIPS subtracts up to 1 cm from the size range — so a 62 cm rider can lose access to MIPS entirely.

On the Lumos Ultra, MIPS is built in as standard at XL. The full 61–65 cm range stays intact. You don't have to choose between rotational protection and a helmet that fits.

Return policy

Large-head shopping means one return is likely. Under 30 days is a red flag.

We give you 30 days from ridelumos.com.

Our Recommendation: Lumos Ultra (XL)

We make the Ultra in XL because the lineup of well-made, modern, US-available helmets that genuinely fit a large head is shorter than it should be.

We wanted to be on that list.

What you get

Why it matters for large-head riders

Most XL helmets feel like an apology. Fewer colors. No smart features. Basic dial. And on too many brands, choosing XL means losing MIPS entirely.

The Ultra XL goes the other way. MIPS comes standard. Full 61–65 cm dial range. Every feature from our smaller sizes — same lights, same turn signals, same app integration.

That matters because the CDC reports head injuries are responsible for the majority of US bicycle fatalities, and visibility to drivers is one of the most reliable ways to keep a crash from happening in the first place.

Large-head riders shouldn't have to give up either layer of protection.

One more thing: our Accident Replacement Program

If you crash in your Ultra within 2 years, we'll replace it at 30% off.

We back it because EPS foam doesn't recover from impact — even one crash means the helmet is done. We'd rather get you back on the bike in a new one than have you ride a compromised shell.

From our riders

"Best fit I have ever gotten in a helmet."
— Ultra MIPS owner, age 71

A chunk of foam was missing from her Ultra after a crash. Her head was completely unharmed.
— Customer review

Lumos Ultra

Smart helmet with 94 LEDs, turn signals, auto brake lights, and MIPS. 22 vents keep you cool on long rides. 370g. IPX6 waterproof. Up to 10hrs battery life.

Buy now

When the Lumos Ultra XL Isn't Right for You

If we told you our helmet fits everyone, you shouldn't trust us on anything else.

Here's where the Ultra honestly isn't the right call:

Above 65 cm

True specialty-fit territory. Search specifically for helmets rated to 66 cm or higher — and read the centimeter spec, not the size label.

Aggressive trail, enduro, or downhill

The Ultra is built for road, commuting, e-bike, and gravel. Technical singletrack needs a half-shell trail helmet with extended rear coverage and a different impact profile.

Wear the right helmet for your ride, not the wrong one with our logo on it.

Very round or wide-temple heads

The Ultra is built on an intermediate-oval mold. Round-head riders sometimes report temple pressure.

That's exactly what the 30-day return is for.

FAQs

What's the biggest bike helmet size made?

Most mainstream bicycle helmets cap at 64–66 cm. Above that, you're looking at skate-style certified helmets or specialty oversized models.

Should I size up if I'm between sizes?

Usually not. A too-big helmet cinched down with the dial sits high — exactly the mushroom problem you're trying to escape. Find a helmet whose cm range covers you in the middle, not the edge.

Does the Ultra XL come without MIPS?

No. The Ultra XL ships with MIPS as standard — there is no non-MIPS option at this size. We made that decision deliberately: at the size range where users are most likely to be wearing a borderline-fit helmet, the rotational protection layer matters most.

Why does my helmet sit on top of my head?

Almost always shape or depth — not circumference. Removing the top pads (keep the side pads) can drop the shell 3–5 mm, which often solves it.

Can I swap pads to fit better?

Yes — thinner top pads to drop the shell lower is a legitimate adjustment. Don't pack extra padding around the sides to force a too-big helmet to feel secure. That compromises crash performance.

How often should I replace my helmet?

Every 3–5 years, or immediately after any impact — even if the shell looks fine. EPS foam degrades over time, and crushed foam can't recover. If you crash in a Lumos within 2 years, our Accident Replacement Program gives you 30% off a new one.

Ready to Stop Returning Helmets?

If your head measures 61–65 cm, the Ultra in XL was built for you.

MIPS standard. Full lighting and turn signals included. 30-day returns. 1-year warranty plus accident replacement.