To make sure that a helmet fits you snuggly and properly, you need to go through the bike helmet size chart. Through the help of bike size data of different brands available, we have made this guide to help you make the right decision.
It includes a step-by-step guide on size charts from multiple brands, including Giro, Bontrager, Bell, Nutcase, etc. So, let’s dive right into the main discussion without any further ado:
Detailed Bike Helmet Size Chart For Beginners
Standard Sizing Parameters
The standard size parameters for bike helmets according to multiple brands go as under:
- Extra small: below 20” or (51cm)
- Small: (51cm–55cm) 20″–21.75″
- Medium: (55cm–59cm) 21.75″–23.25″
- Large: (59cm–63cm) 23.25″–24.75″
- Extra-large: (63cm) above 24.75″
One size fits all: has a highly adjustable fit system but be sure to try it out before buying.
Based on these parameters, we take a look at the bike sizing chart of multiple brands as under:
Giro Helmet Size Chart
Being one of the most popular and reputable helmet brands, Giro offers some amazing mountain bike helmets and road bike models that will fit your head with due comfort and convenience.
While purchasing a Giro helmet, keep these size chart metrics in mind:
| Size | Size in Centimeters | Size in Inches |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| M | 55-59 | 20-23 |
| L | 59-63 | 23-24 |
| XL | 63-65 | 24-25 |
| XXL | N/A | N/A |
That’s the standard sizing of Giro helmets. However, the brand does offer some exceptions.
For instance, the size increases for full-face bike helmets as they may run narrow due to their internal padding and other accessories.
Similarly, Giro also offers universal sizing that includes a circumference ranging from 50 to 57 cm for women, 54-61 cm for unisex helmets, and 58-65 cm for extra-large heads.
Nutcase Helmet Size Chart
Nutcase helmets are also quite popular in the United States. The major reason for its popularity is that these helmets are durable, they feature a unique design, and most Nutcase models have MIPS technology integrated with them.
Here is a complete size chart for those riders who want to get themselves a Nutcase helmet:
| Size | Size in Centimeters | Size in Inches |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| M | 55-59 | 20-23 |
| L | 59-63 | 23-24 |
| XL | 63-65 | 24-25 |
| XXL | N/A | N/A |
Not to mention, Nutcase offers helmets for small babies as well. Their sizes in centimeters might range from 48 to 52, and in inches, the size converts from 18 to 20.5 inches.
Bern Limited – Helmet Size Chart
Bern also specializes in making helmets that could keep your head protected, especially when involved in a crash.
The good thing about the brand is that you’ll find multiple sizes ranging from extra small to extra-extra-large and check whether they go side by side with your head’s circumference or not.
The table goes as under:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
Scott Bike Helmet Size Chart
Scott is a well-renowned brand for producing full-face, open-face, and daily commute biking helmets.
The size chart for Scott helmets is as follows:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
Lazer Sport – Helmet Size Chart
Lazer is a global brand specializing in cycling helmets that ensure complete head and skull area protection.
The sizing chart that this manufacturer offers is as under:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
Thousand – Helmet Size Chart
Specializing mostly in traditional helmets, Thousand offers full-face helmet models that can keep your breathability intact while protecting your head from impacts and damage.
The bike size chart for this brand goes as under:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
Bontrager Road Helmet Size Chart
Another brand is famous for producing mountain bike helmets, both open and full-faced helmets.
The manufacturer allows you to choose from a variety of helmets based on the circumference of your head.
Bontrager offers the following sizes:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
Bell Helmet Size Chart
Bell is a pioneer in making comfortable and snug helmets that would ensure protection against rotational forces as well as sudden impacts.
The size range for this brand goes as under:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
TeamObsidian Helmet Size Chart
Not as famous as the likes of Bontrager or Bell, TeamObsidian helmets are surely making their place in the market.
The complete size chart that this helmet manufacturer offers can be found below:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
Smith Adult Helmet Size Chart
We already know MIPS protects you better than non-MIPS helmets. This is why Smith produces helmets with MIPS integrated with them to ensure that your head and brain remain conscious in case you go through a serious fall.
The helmet size chart for the adult category goes as under:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
Related: Bike Helmet Buying Guide for Beginners
Smith Junior Helmet Size Chart
Like the adult category, Smith has also focused on manufacturing helmets for teenagers and toddlers.
The sizing category for youth is as follows:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
Garneau Bike Helmet Size Chart
Garneau produces bike helmets for women, men, youth, and children simultaneously. The models have usually got a unique shape, and durable body, and can protect a rider from harsh incidents at the same time.
The sizing chart for Garneau is as under:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
iOutdoor Bike Helmet Size Chart
Last but not least, iOutdoor is also famous for producing some of the best MTB helmets with a snug and comfortable fit.
We take a look at the sizes it offers as under:
| Size | Size in Centimeters | Size in Inches |
| XL | 63-65 | 24-25 |
| XS | 45-49 | 17-19 |
| S | 51-55 | 20-21 |
| L | 59-63 | 23-24 |
| M | 55-59 | 20-23 |
| XXL | N/A | N/A |
How to Measure Head for Bike Helmet?
You’ll need to start by taking multiple measurements of your head, followed by finding the right size of the helmet from different manufacturers.
But, the whole process will certainly become easier in this guide. Let us get started with how to measure the head circumference to get to the right size first:
Determining Your Head Size:
Measuring the head size means you’ll get to measure the circumference of your head and then match it with the available sizes present in the market.
You’ll need a tape measure or a charging cable, or simply a string to get started with the whole process. We’ll also recommend keeping a ruler by your side if you use a charging cable or a string.
The whole process of how to size a bike helmet goes as under:
Step 1: Measure the Circumference of Your Head:
Wrap the measuring tape around your head in a way that it’s one inch above your eyebrows and take the first measurement of the circumference of your head.
Note it down and take two more head measurements to find the average size accordingly. In case you don’t have a measuring tape available, use either a charging cable or simply a string to measure the circumference of your head.
You can measure it later with the help of a ruler. We’ll still recommend that you use a measuring tape for correct measurements.
Step 2: Try the Helmet Yourself
Go to a local bike shop and start wearing helmets according to the circumference measurement of your head. Make sure that you wear the bike helmet the right way.
The helmet should not move when you move your head abruptly. If it moves, you are wearing a helmet that’s way too large for your head. Keep trying the helmets, and you’ll finally find the one that will fit snuggly.
Step 3: Determining a Proper Fit
The last thing to check after you wear the helmet is to see whether it fits properly or not. In that aspect, the helmet should sit right above your eyebrows. As far as the backside is concerned, it should not touch the nape of your neck.
Adjust the chin straps in a way that there’s a distance of only two fingers in between. Check the helmet again by moving your head here and there, and if it does not move, you have found a perfectly sized helmet for your head.
People Also Ask:
How do I know my bike helmet size?
Start by measuring the circumference of your head with a measuring tape. After that, find the closest option available and put it on. It should fit snuggly and not slide after you adjust the chinstrap. If you feel that the helmet is too narrow or wide, go for another sizing option.
What size helmet is 53cm?
53cm or 20 inches fall into the small size category. Bikers with a small head circumference usually go for such helmets as they offer a comfortable and snug fit without any hassle.
What size helmet is 57cm?
The 57cm marks fall into the medium category, and bike helmets with this type of sizing are a bit wide compared to the small size. They could also ensure a snug fit for riders with medium head sizes.
Final Takeaways
The bike helmet size chart from multiple brands does not offer a 100% guarantee that the exact helmet will fit you.
That’s one of the reasons we, as well as all helmet manufacturers, recommend visiting a local shop first to try a helmet practically and determine the size accordingly.
Once it’s sorted out, you can keep ordering the same size for the rest of your life unless you are not a kid.
Good Luck!!
