How to Choose a Bike Helmet? (Beginner’s GUIDE) [2021]

How to Choose a Bike Helmet

A bike helmet is the #1 bike accessory you should buy. This article teaches you how to choose a bike helmet based on your riding style and needs.

I will explain how to choose the right helmet size, the differences, pros & cons between bike helmet types, and the other features you should consider.

Let’s get into it.

How to Choose a Bike Helmet? Two Things to Consider

When buying a new helmet, two things are the most important. The right:

  1. Size
  2. Type

The other bike helmet features like weight, ventilation, design, etc., are worth considering once you know the helmet will fit you and it is the right type for your riding style.

1. How to Choose the Right Bike Helmet Size?

Every bike helmet manufacturer has different sizing. The helmet’s size is determined by the head circumference in inches or cm.

Use a soft tailor tape measure to measure it.

Once you know your head circumference’s size, choosing the correct helmet size is pretty easy.

The most common adult bicycle helmet sizes are:

  • XS: below 20″ | below 51cm
  • S: 20–21.75″ | 51–55cm
  • M: 21.75–23.25″ | 55–59cm
  • L: 23.25–24.75″ | 59–63cm
  • XL: above 24.75″ | above 63cm

NOTE: These sizes differ based on the manufacturer.

What if you are between two sizes?

If you are between two sizes, you have multiple options.

  • You can buy a larger helmet and adjust the size with a dial. If it is still too big, you can wear a cycling cap.
  • Go for the smaller one and deal with the fact that you won’t fit a cycling cap underneath.
  • Find another helmet that has different sizing.

It is always better to try the helmet in person to ensure you buy the right size.

How do I know the helmet fits?

The helmet should feel just right. It shouldn’t be too tight or loose. Also, double-check the official recommendations by the National Highway Traffic Safety Administration.

  • Two finger-width should be between your eyebrow and the helmet.
  • The side straps should form a “V” shape under and slightly in front of your ears.
  • The buckle should be centered under your chin, and it should be tight enough, so you don’t snug one or two fingers underneath it.
bicycle helmet fit
The helmet of this racer fits properly

You might also be interested in these bicycle safety tips.

2. Pick the Right Type of a Bike Helmet

There are three main types of bike helmets – road, mountain, and commuter (recreational, urban). They differ mostly in their appearance, ventilation, weight, protection, and aerodynamics.

Types of bike helmets (mountain, road, commuter)
Types of bike helmets

Let me describe them one by one.

Road Bike Helmets

Road bike helmets are designed for road cycling. They are lightweight to ease the pressure put on your neck muscles during long rides. They are also well-ventilated, so your head won’t overheat during hot summer days. And, they are aero optimized to save precious seconds when racing.

types of road bike helmets

The importance of the three features described above differed based on the road bike helmet type.

  • Standard road bike helmets are designed to be lightweight and well-ventilated but they are not as aerodynamic as aero road bike helmets.
  • Aero road bike helmets are aerodynamic but their ventilation is worse than standard road bike helmets. They also tend to be a little heavier.
  • Time trial helmets are niche-specific. They are more aerodynamic than aero road bike helmets. They are used only for time trials or triathlons. Due to their aerodynamic shape they are the heaviest type of road bike helmets.

The following table shows the pros and cons of road bike helmet types.

Type of road bike helmetProsConsRecommended for
Standard• Well ventilated
• Light
• Less aerodynamic• Summer months
• Casual road cyclists and pros
Aero• More aero• Less ventilated
• A little bit heavier
• Pros, racers, eventually time trialists and triathletes
Time trial• Most aero• Worse ventilated
• Heavy
• Time trialists and triathletes

Mountain Bike Helmets

MTB helmets provide better protection in terrain than road bike helmets thanks to their design featuring a visor and extended rear and sides. They provide either standard or full-face protection.

types of mountain bike helmets
  • Standard MTB helmets look like road bike helmets but they also feature a visor to protect your face against branches, dirt, and sun. Additionaly, they better protect your nape. They are lightweight and well ventilated, but don’t provide a full-face protection.
  • Full-face MTB helmets feature a chin protector. They are ideal for highly technical terrain like trails and downhills. Some full-face helmets have removeable chin protector, so you can use them as a standard MTB helmet.
  • Dirt jump and BMX helmets are niche specific. They look like skateboard helmets–they have simple round design and average ventilation. Thanks to their extended rear side, they better protect nape.

Commuter Helmets

Commuter helmets, also sometimes called recreational or urban helmets, are ideal for people who commute to or from school, work, etc., or want an affordable helmet for occasional bike trips.

types of commuter bike helmets
  • Standard commuter helmets are a budget alternative to road and MTB helmets. Thanks to their good ventilation, they are suitable for casual bike trips.
  • Skateboard-style commuter helmets are inspired by skateboard helmets. They are more stylish and sometimes feature a visor or in-build LEDs, but they are not as well ventilated.

Bike Helmets Features

In this part, you learn more about current trends and bike helmet features.

bike helmet parts
Bike helmet parts | Product picture credit: Rockbros


Every bike helmet sold in the USA should have the Consumer Product Safety Commission (CPSC) certification. In Europe, there is the so-called EN 1079 standard, in Australia and New Zealand AS/NZS 2063, etc.

The purpose of these certifications is to verify that the helmet meets the safety requirements. Helmets go through a series of testing. Watch the following video to see a few examples of these tests.

TIP: Virginia Tech impact-tests bike helmets and gives them star ratings. Check out their website for more info.

Extra Safety Features: MIPS, SPIN, WaveCell

Some helmets feature extra safety technologies that reduce the rotational and/or linear forces and strain levels during an impact. The following technologies are the most widespread:

  • MIPS (Multi-directional Impact Protection System)
  • SPIN (Shearing Pads Inside)
  • WaveCell

Their main goal is to reduce the risk of a brain injury and further improve your head protection.


MIPS technology was developed and researched for more than 20 years. Helmets with MIPS reduce the forces that arise during an impact and are then transmitted to the brain.

Reducing the rotational forces means the risk of brain injuries is minimized. Take a look at the following picture of the strain level for illustration.

MIPS strain level 1
Comparison of strain-level when using MIPS and standard helmet | Source:

MIPS allows the head to move 10-15 mm inside the helmet. This reduces harmful rotational motion that would otherwise be transferred to your brain and cause injuries.

The movement is possible thanks to the inside construction. Watch the following video to learn more.

How does MIPS work?

What is the MIPS downside?
The main downside of bike helmets with MIPS is the weight. These helmets are heavier for about 0.88-1.59oz. (25-45g). MIPS also does not reduce linear forces.


SPIN (developed by POC) is similar to MIPS. There are some differences, though. Unlike MIPS, SPIN uses SPIN pads that reduce rotational and linear forces. The following animation illustrates it well.

SPIN technology explained


WaveCell is a cellular structure inside of a helmet that reduces impacts and rotational forces. It is used by Bontrager helmets.

WaveCell technology explained

How does WaveCell work?

Trek explains the WaveCell technology in 3 steps:

  1. Flex – reduces the initial frictional forces.
  2. Crumple – reduces the impact forces.
  3. Glide – the WaveCell redirects the energy aweay from your head.

What is the WaveCell downside?
Similar to MIPS, WaveCell also adds around 1.76oz. (50g) to the helmet’s weight. Furthermore, WaveCell technology is used on Bontrager’s helmets only. They are also more expensive than MIPS or SPIN helmets.

Ventilation vs. Aerodynamics

A well-ventilated helmet is important for hot summer days. The last thing you want to experience on a bike is head pain caused by overheating.

The general rule of thumb is:

The better ventilation = the worse aerodynamics and vice versa

Aerodynamic helmets have worse ventilation to improve airflow and aerodynamics. They may be good for short distances or fast-paced races, but not for climbing or hot days.

img 2900b
Kask Valegro – well-ventilated helmet | Source:
9 12 protone sim 3D 22
Kask Protone – semi-aero helmet | Source:
img 2897b
Kask Utopia – aero helmet | Source:

If you don’t hunt every second, I recommend buying a standard, well-ventilated helmet especially, if you value comfort over speed.


The bike helmet’s weight is an important factor if you make long-distance trips or are a road cyclist.

Lightweight bike helmets (under 0.55lb / 250g) don’t put as much pressure on your neck muscles so that you won’t experience neck pain.

But, this doesn’t mean you should use a road cycling helmet for downhills. Make sure always to prefer sufficient protection!

Bike Helmets FAQ


All helmets sold in the US or in the EU have to pass certain quality standards and have certification (CPSC, EN 1079, AS/NZS 2063, etc.), so you don’t have to be afraid that a cheap helmet won’t protect you.

Therefore, when choosing a bike helmet, make sure you choose the right type and size. The color and design are up to your preference.

To choose the right helmet size, measure your head circumference with a tape measure. If you are between two sizes, choose the larger one. Buy a helmet with an adjusting dial for a better fit.

When choosing the helmet type, think about your riding style.

  • Road bike helmets are designed for road cycling. They are lightweight, well-ventilated, and aero.
    • Standard road bike helmets are lighter and better ventilated than aero road bike helmets. They are suitable for the most riders.
    • Aero road bike helmets are more aero than standard helmets. They are ideal for racers or people who chase every second.
    • Time trial helmets are the most aero, but due to their weight and bad ventilation, they are only suitable for time trialist or triathletes.
  • Mountain bike helmets are ideal for mountain bikers or people who make bike trips. They are well-ventilated and based on the type are also lightweight and feature a sun visor.
    • Standard MTB helmets are suitable for most mountain bikers except for those who prefer highly-technical and dangerous terrain.
    • Full-face MTB helmets are perfect for technical terrain because they also provide protection to your chin and nape.
    • Dirt jump and BMX helmets look like skateboard helmets. Go for them if you plan to do one of these disciplines.
  • Commuter helmets are perfect for commuters and occasional riders. They look stylish to fit with your more casual outfit.
    • Standard commuter helmets are affordable, decently ventilated ideal for casual cyclists and daily commuters.
    • Skateboard-style commuter helmets are stylish helmets perfect for people who prefer elegant over sporty look.

I hope this article will help you choose the right bike helmet. If you find it useful, please, consider sharing it or leaving a comment below.

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