Everything you should know before you purchase your kids bike helmet – including size chart

We bought a bike as a surprise for our daughter and we needed to get her a helmet and accessories too. As it was a surprise for her birthday we’d pondered over what size helmet to get? Below we have collated the information we found with the recommended size you may need.

12 MONTHS46 CM – 18.1 INCH45 CM – 17.7 INCH
18 MONTHS47.5 CM – 18.7 INCH46.5 CM – 18.3 INCH
2 YEARS48 CM – 18.9 INCH47 CM – 18.5 INCH
2.5 YEARS49 CM – 19.3 INCH48 CM – 18.9 INCH
3 YEARS49 CM – 19.3 INCH49 CM – 19.3 INCH
3.5 YEARS50 CM – 19.7 INCH49 CM – 19.3 INCH
4 YEARS50.5 CM – 19.9 INCH49.5 CM – 19.5 INCH
4.5 YEARS51 CM – 20.1 INCH50 CM – 19.7 INCH
5 YEARS51 CM – 20.1 INCH50 CM – 19.7 INCH
6 YEARS52 CM – 20.5 INCH51 CM – 20.1 INCH
7 YEARS53 CM – 20.9 INCH52 CM – 20.5 INCH
8 YEARS54 CM – 21.3 INCH53 CM – 20.9 INCH
 *for reference only

The importance of buying the correct size helmet is key to ensuring your child’s safety on a bike. We researched endlessly to get it right and ways to ensure we had and here’s what we found. 

How To Measure Your Kids Head
Things To Consider 
How To Fit Your Kids Helmet Correctly 
Importance Of Wearing A Helmet 

How To Measure Your Kids Head 

It’s essential that you get the right size helmet for your kid. You need to choose the right size that is going to fit snugly. The general consensus when buying kids clothing is to ‘buy a size bigger’, that’s definitely NOT the case when buying a bike helmet. 

For the helmet to work to its full safety capacity, the size needs to be perfect. Getting a helmet too small or too big can greatly reduce this. 

The correct way to ensure you are getting the correct size is to measure your kids head circumference. This needs to be done about an inch above their eyebrows. The measurement needs to be snug, not too tight, not too loose. 

In case you are like we were and the purchase of your kids’ bike helmet needs to be a surprise, you could make a hat with them and in the process get a measurement reference you can later check. Use a piece of string for the measuring and check the size against a tape measure. 

In case you have no way of measuring, I’ve put a reference guide table above.  

Things To Consider 

What sounded like a simple task, buying a helmet for your kid is certainly no easy feat. After all we are buying this for our kids’ safety, and we’ve got every right to be picky.  

Once you are ready with sizing there are many other things you can consider which can help to narrow the search down. 

Construction (Making of the helmet) 

There are two main types of construction to choose from, hard-shell helmets and in-mold helmets. 

Both offers perfectly adequate protection for your child in the event of an accident. They differ in style with durability and the number of vents. 

Hard-shell helmets have a thin layer of tape around the middle section. This covers the rough edges of the plastic shell for comfort whilst using. In-molds have an inner foam with a fused outer plastic shell.  


Good resistance to penetration and impactCould crack and warp if left in the heat
Highly durableHeavier and bulkier
ASTM Skateboarding CertificatedHas less room for vents


lightweightslightly less durable
has more room for more ventsNot ASTM Skateboarding Certified

Number of Vents in Helmet 

We need to remember that they will be wearing the helmet when doing a physical activity. Which probably means your child will sweat. If you’ve ever worn a helmet yourselves you’ll know it can get quite warm if you’ve not got enough vents.  

Vents increase the airflow in the helmet and makes the whole experience much more comfortable. Traditional bike helmets have more vents compared to skater helmets for example. 

Standard Bike Helmet Design or Skater Style Helmet Design? 

The style choice will more than likely boil down to these two design options. There’s only a slight difference between them both.  

A traditional standard bike helmet is lighter and easily adjustable, it is this style which is recommended for kids who mainly ride bikes. With the vents it is also a good choice for riding in hot weather. It does offer less protection to the lower back of the head and it doesn’t have as many style options.

The skater helmet design is much bulkier and offers better head coverage. You will find more styles options with this design. Its dual certified also. With that said you will have less ventilation and it will be heavier. 

Safety Certificates  

All helmets must undergo safety standards checks to ensure their effectiveness. Make sure it has the CPSC (Consumer Product Safety Commission) sticker if buying in the US. This will more than likely be located inside the helmet. All helmets produced in the US are expected to follow these standards set. Something to also be aware of is that not all CPSC stickers look the same, so don’t worry if it looks different to another. 

You’ve also got the pre mentioned ASTM for skater style helmets. If buying this type of helmet this should be dual certified with both CPSC and ASTM. 


Especially with a kids’ helmets the buckle is of mass importance. Standard buckles work just fine on any helmet but if it’s not a good fitting buckle it will not be comfortable. You can get helmets with pinch free buckles. Standard buckles have a plastic guard underneath. On higher end helmets you will find more advanced magnetic locks. 


We’re not biking in the house so its inevitable that your kid at some point is going to be in direct sunlight. Visors will help to shield your kid’s eyes from the sun and from dust.  

Most Standard design helmets come with built in or an ability to clip them on. Skater style however do not have this facility due to their heavier bulkier design. 


You’ve got the sizing right and to make it more comfortable and ensure fitted correctly most helmets come with built in adjustable systems. They are usually internal cages made of plastic with the capability to adjust so that they fit your kids head perfectly. 

Kids have different shaped heads and this internal system allows the helmet itself to conform to your kid’s head. This will then allow the helmet to stay in place to better help protect your child’s safety. 

There are three different types of internal adjustment systems: The traditional Dial Adjust, Lazer Self Adjust and Pad with adjust.  

It’s important to remember that although you can adjust some helmets, you must still ensure you have purchased the correct size as discussed above. 

How To Fit Your Kids Helmet Correctly

We’ve bought the right helmet, put air in the tyres and fitted those training wheels. Now we need to fit the helmet correctly before they go cycling. I’ve put below a simple 4 step guide to do this correctly: 

1: Position The Helmet 

Place the helmet low on your kid’s forehead. The gap between the helmet and the eyebrows should be approx. one to two fingers. This will make sure they can still look upward but is enough to protect the forehead. 

2: Rotate the Helmet 

Doing this quick step, you can ensure it is fitted correctly. If your kid’s eyebrows shift with the helmet it’s a good fit. If it slides about easily the helmet is most likely too big and may just need adjustment. 

3: Adjust The Side Straps 

Once you’ve got a good fit you should check that the right and left strap both meet below your kids chin. They should form a ‘Y’ shape. You can adjust these on each side as required. 

4: Fasten  

Fasten making sure the chin strap doesn’t pinch. Ask you kid to open their mouth and it should tighten. This is a good sign of a good fit. If not refer to step 3 to adjust. 

Here’s a clip that you might find helpful to help fit or adjust. 

Importance of Wearing a Helmet 

Most people really underestimate the importance of their kids’ wearing helmets.  

All accidents are unexpected but can occur at any time. Cycling is considered to be a generally safe activity and most kids and toddlers really enjoy the experience, but regardless accodents do happen and approximatley 300,000 kids visit the emergancy room due to bike related accidents each year.

Properly fitted helmets quite simply dramatically reduce the risk of injury in the event of any unfortunate, unforseen accident.

The technology used in making these helmets features a layer of impact-absorbing foam around your child’s head/brain. 

The designed puncture-resistant shells play a vital role in protecting our kids neck and head if they were to fall to the ground.  

Many studies have shown that a good helmet can reduce the risk of head injuries by as much as 80%. 

The Warburton Family

Everything we write is tried and tested. We research everything before putting it out to the world. Thanks for reading :-)

Recent Posts