What Size Bike Helmet Should I Get?

What Size Bike Helmet Should I Get?

We’ve said it before, and we’ll say it again: nothing is more important than a properly fitting bike helmet. This cycling safety rule should always be at the forefront of your mind.

But here’s the question: What size bike helmet should you get? It may seem like an easy inquiry, but finding the perfect fit can be a bit more complex than you might think.

Ill-fitting helmets can compromise your protection, comfort, and overall cycling experience. That’s why we’re here to guide you through the process to ensure you’re safeguarded every time you hit the road or trail.

Bike Helmet Sizes

Starling Bike Helmet Olive 

When it comes to bike helmets, size matters - that counts for toddler bike helmets, kids cycle helmets, and adult cycle helmets too. Not only does this ensure comfort, but it also provides the needed protection. To get it right, understanding the significance of helmet sizes helps.

Bike helmet sizes refer to the range of head circumferences a helmet is designed to fit. A helmet that is too loose might slip off, while a helmet that is too tight can cause discomfort or pressure points.

The sizing systems can vary depending on the manufacturer and brand. But there are two common sizing widely used:

  • Circumference-based sizing. This system relies on the measurement of your head circumference, in cm or inches. The helmet’s inner circumference should match your head size. Use a size chart provided by the manufacturer to measure.
  • Head shape-based sizing. Some manufacturers take into account head shape variations. Different head shapes (round, oval, or intermediate) may require different helmet models. This is true even if the head circumference falls within the same range. Manufacturers may offer models specifically designed to accommodate various head shapes.

Bike helmets are usually labelled with size descriptors: small, medium, large, or extra-large. Corresponding measurements, either head circumferences or dimensions often accompany these labels. This helps you determine the right size for your head.

For instance, a small-sized helmet is suitable for 52cm to 56cm (20.5 to 22 inches). A medium-sized helmet could cover head circumferences of 56cm to 59cm (22 to 23.2 inches). While a large-sized helmet may accommodate head sizes from 58cm to 63cm (23.2 to 24.8 inches).

These measurements provide a general guideline for finding the correct size. But always refer to the specific manufacturer’s size chart for precise measurements.

Measuring Your Head

Metric Helmet Gloss Plum 

To get the correct size for your bicycle helmet, you’ll need to measure your head accurately. Follow these step-by-step instructions to ensure precise measurements:

1. Gather the necessary tools

  • A flexible measuring tape or a piece of string and a ruler.
  • A mirror or ask someone for assistance to ensure accurate positioning.

2. Prepare for measurement

  • If you have long hair, tie it back or flat it to avoid any interference with the measurement.
  • Wear a thin cloth or no cloth on your head to ensure accurate measurements.

3. Position the measuring tape

  • Place the measuring tape or string around your head, just above your eyebrows. Wrap it around the widest part of your skull.
  • Make sure the tape is level and snug but not too tight or too loose. It should sit comfortably on your forehead and the back of your head.

4. Read the measurement

  • Take note of the measurement in centimetres or inches. This will depend on the measuring tape or string you used.

5. Repeat for accuracy

  • Perform the measurement a couple of times to ensure consistency and accuracy. Take the average of the measurements for the most precise result.

Tips for accurate measurements:

  • A soft, flexible measuring tape is ideal for obtaining accurate head measurements. If you don't have one, use a piece of string and then measure the string with a ruler.
  • Place the tape or string just above your eyebrows and wrap it around the widest part of your head. Ensure that it’s parallel to the ground and sits straight across your forehead.
  • The tape should be snug against your head without exerting excessive pressure. A comfortable and secure fit is crucial for both safety and comfort.

By measuring your head correctly, you can ensure a proper fit. This, in return, maximises both safety and comfort during your cycling adventures.

Determining the Right Helmet Size

Mirror Mirror Bike Helmet Bronze 

Now that you have measured your head, it’s time to determine the appropriate size for your bike helmet.

Most helmet manufacturers provide size charts that correlate head measurements with helmet sizes. Locate the size chart specific to the helmet brand and model you are interested in. Find the range of head circumferences or dimensions that corresponds to your measurement.

If the measurement falls within a specific range on the chart, select the corresponding helmet size. But if it falls between two sizes, consider the following factors to determine the best size:

  • Opt for the smaller size if you prefer a snugger fit. Or if you’ve measured accurately and the size falls within the manufacturer’s recommended range.
  • Choose the larger size if you prefer a more relaxed fit. Or if the smaller size is at the upper limit of the manufacturer’s recommendation.

Keep in mind that helmet fit can vary between brands and models. If possible, try on different helmet sizes within the recommended range. This will help you determine which one feels the most comfortable and secure. Also, consider the helmet’s adjustability features, such as retention systems and straps. This can help fine-tune the fit for added comfort and stability.

Here’s an example of a size chart:

Helmet Size

Head Circumference (cm)

Head Circumference (inches)













Note: The above size chart is just an example. Please refer to the manufacturer's size chart for accurate measurements and size ranges.


Choosing the right size bike helmet guarantees your safety and comfort while cycling. To select the perfect fit:

  • accurately measure your head
  • refer to the manufacturer’s size chart
  • consider personal preferences

Prioritise your safety by investing in a bike helmet that fits you just right. Your head deserves nothing less than the best. Ready to shop? Get your toddler bike helmet, kids cycle helmet or adult bike helmet

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