How to Measure a Bike Helmet

How to measure for a bike helmet

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Bike helmets are a must-have these days. 

Not because there’s a high chance that you’ll fall from your bike but because it’s essential to be ready for anything, even if it means a worst-case cycling scenario. After all, safety must be a number one priority, which means wearing a helmet is important now than ever before. 

However, there’s one big problem when it comes to choosing the best bike helmet: 


You see, you really can’t decide if a helmet will fit your head by merely looking at it. Even if it’s made of the finest material and promise all the comfort in the world, it won’t give if it can’t fit. 

But the sizing isn’t nearly as hard to get right. So in this article, we’ll teach you how to measure a bike’s helmet so you can get the right size the first time. 

Let’s get started.  

Why Size Matters

Getting the right helmet is very important because it goes a long way to ensure you get as much safety assurance as possible in the event of an accident. 

A helmet that is too big for your head could easily fall off when a crash happens, exposing your head to serious or even fatal injury. 

One that’s too small for your head would feel uncomfortable, making it impossible for you to enjoy your ride. Plus, in the event of an impact, it might not have the desired protection. 

But if the helmet fits well, you can be confident that it will evenly distribute impact in the event of an accident and keep you safe. 

How to Measure For A Helmet the Right Way 

You want to get a helmet of the right size from the start. And the best way to do that is to start by knowing the circumference of your head. The result will help you choose a helmet that fits well straight out of the box. 

Take a clothing tape measure and take it across your head. Make sure you place the tape approximately an inch up from the eyebrows. You can use a string if you don’t have a tape measure, then transfer the length to a ruler to get the measurement. Make sure the measurements are accurate. 

With this information, you can visit a bike shop nearby and use it to get a good helmet. 

It’s important to understand that different manufacturers have different ways of interpreting the right size for given head circumference. So it is not necessarily a one-chart-fits-all. 

Below is a sample of a chart used to get the best helmet size.

Head size (centimeters)

Helmet size

52cm – 56cm

S (Small)

56cm – 60cm

M (Medium)

60cm – 64cm

L (Large)

There are also one-size-fits-all helmets, which, regardless of the size, one simply adjusts an inner strap until the helmet gets the right snug. 

One-size-fits-all helmets

One-size-fits-all helmets have proven to be equally useful in easing the process of getting the right size of a helmet. You only place the helmet on your head, then tighten the inner strap using a knob or dial at the back of the helmet until it fits right. 

This is a good alternative as it saves you the time of trying a bunch of different helmet models just to find a good fit. This also means you don’t have to buy a new helmet if your head size changes in the future. 

However, one-size-fits-all helmets have also been blamed for requiring one to fix the ring so tight that it feels like it’s squeezing the head, not to mention that loosening them a little gets them sloppy on the head.  

On the other hand, they have received praise because they’re very easy to adjust. They also arguably require lesser padding to boost the snug, hence allowing more airflow when in use. The ring also doesn’t lose its efficiency due to sweating.  

Trying a New Helmet

Try on the new helmet to check if it nicely fits on your head. It should be well leveled on your head, not slanting backwards. 

The helmet should not be more than two fingers away from your eyebrows. Take a test by shaking the head and if it easily moves from side to side, then you know it’s a big helmet. You can stop it from moving forward by adding your own padding. At least this will make it fit better. 

Measuring Helmets for Kids

When it comes to kids, getting the right helmet needs the guardian to provide guidance. Parents ought to continue emphasising on the importance of helmets to their children to avoid them refusing to wear it every time they take their bikes out for a ride. 

Sometimes, the idea when getting any wear for children is that even if the clothing is slightly big, then there is nothing to worry about since they’ll grow into it. But you simply can’t apply the same analogy when it comes to bike helmets. In fact, for a helmet to be effective, it must fit from the start. 

The process of measuring the helmet for children is similar to that of adults. If you are unable to know the measurement, you can easily tell their estimated measurement using their age. 

Below is a chart that can guide you:




12 months

46 cm

45 cm

18 months

47.5 cm

46.5 cm

2 years

48 cm

47 cm

2.5 years

49 cm

48 cm

3 years

49 cm

49 cm

3.5 years

50 cm

49 cm

4 years

50.5 cm

49.5 cm

4.5 years

51 cm

50 cm

5 years

51 cm

50 cm

6 years

52 cm

51 cm

7 years

53 cm

52 cm

8 years

54 cm

53 cm

Once you have the right measurements for your child, use the data to get the right helmet from the bike shop. Alternatively, you could visit the shop with your kid and try out various helmets together until you get a size that fits.

As your child tries out different helmets, be sure to ask them how they feel. This will make it easy for you to know if the fit is correct or otherwise.

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