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 should you get?

It may seem simple, but finding the perfect fit can be more complex than you think. We’re here to guide you through the process to ensure you’re safe every time you hit the road or trail. Ready?

[Table: Cycle Helmet Sizing]

Cycle Helmet Size Guide

 

(Starling Bike Helmet Olive)

Bike helmet sizes refer to the range of head circumferences a helmet is designed to fit. A too-loose helmet might slip off, while one that is too tight can cause discomfort or pressure points. The sizing systems can vary depending on the manufacturer and brand.

Two sizing approaches are:

• Circumference-based sizing: This uses your head measurement in centimetres or inches. The helmet’s internal fit range should match your measurement as closely as possible.

• Head shape-based sizing: Some helmet models suit rounder heads; others suit oval shapes. Two people with the same head circumference may need different models for a secure fit.

Bike helmets are usually labelled with size descriptors: small, medium, large, or extra-large. 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). A large-sized helmet may accommodate head sizes from 58cm to 63cm (23.2 to 24.8 inches).

Use these measurements as a guide, but always check the manufacturer’s chart for the exact size.

How to Measure Your Head for a Bike Helmet

 

 

Accurate measuring makes sizing much easier.

1. Place the measuring tape or string around your head, just above your eyebrows. Wrap it around the widest part of your skull.

2. 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.

3. Note the measurement in centimetres or inches. The measuring tape or string you use will determine this.

4. Perform the measurement a couple of times to ensure consistency and accuracy. For the most precise result, take the average of the measurements.

Bike Helmet Size Chart

 

 

Most helmet manufacturers provide size charts that correlate head measurements with helmet sizes. Below is a general example:

Helmet Size	Head Circumference (cm)	Head Circumference (inches)
Small	52-56	20.5-22
Medium	56-59	22-23.2
Large	59-63	23.2-24.8
X-Large	63-66	24.8-26

Locate the size chart specific to the helmet brand and model you are interested in. Use your measurement to find the matching size range.

What to Do If You’re Between Helmet Sizes

Measurements don’t always land perfectly in one size range. When you’re between sizes:

• Choose the smaller size for a closer, more secure fit.

• Choose the larger size if your measurement sits at the very top of a range or you prefer more room.

• Check the helmet’s adjustment system. Retention dials and internal padding can fine-tune the fit.

Trying both sizes, when possible, gives you the best chance to find what fits your head best.

Head Shape and Helmet Fit

Head shape affects how a helmet feels once it’s on. Signs the shape isn’t right include:

• Pressure at the temples

• Gaps at the sides

• The helmet rocks even when tightened

In these cases, switch to a different model with more size options.

Final Helmet Fit Checks

After choosing a size, check how the helmet sits before riding:

• The helmet should sit level, covering your forehead. It shouldn’t tip back when you look up.

• It should feel snug all the way around, without causing pressure or discomfort.

• Fasten the straps and shake your head gently. The helmet shouldn’t move or slide.

• Adjust the retention dial or system so the helmet stays even and secure.

Remember, a helmet that fits right stays put and doesn’t move around while you ride. If 

you’re ready to shop, browse our selections below:

Next on your reading list: How Should Your Bike Helmet Fit?

FAQs

What size bike helmet should I get?

The right size bike helmet fits your head without being too tight or loose.

Measure your head circumference around the widest part - above your eyebrows and ears. Check the helmet brand’s size chart. Each company lists the ranges for small, medium, and large. Match your number to the chart and pick the size that fits. Sizes can vary between brands, so double‑check before you buy.

How do I measure my head for a bike helmet?

Take a soft tape measure and wrap it around your head. Do so about an inch above your eyebrows, over the widest part at the back. Keep the tape level and snug, not tight.

If you don’t have a tape measure, use a string and then measure the string with a ruler. Once you have the measurement in centimetres or inches, use it to find the right size in a helmet size chart.

What if I’m between bike helmet sizes?

If your head measurement is between two sizes, try both if you can. The smaller size gives a tighter fit, and most helmets have an adjustment dial to make it fit better. The larger size may feel more comfortable if the smaller one is too tight.

Helmet shapes and padding are different across brands. The best way to decide is to try them on and see how they sit with the straps and retention system adjusted.

How tight should a bike helmet be?

A bike helmet should fit snug around your head without pain or pressure points. It shouldn’t be so loose that it rocks or slides when you move your head. If it moves, it’s too loose. If it squeezes your temples or forehead, it’s too tight. The right tightness should allow 1 or 2 fingers to fit through the strap under your chin.

Do bike helmet sizes vary by brand?

Yes, helmet sizes and shapes can differ between brands and even between models. One brand’s medium might fit a slightly different head size than another brand’s medium. Look at each brand’s chart and try the helmet if you can, instead of assuming sizes match.

Does head shape matter when choosing a bike helmet?

Yes, head shape matters because helmets are shaped differently inside. Two people with the same head measurement may find one helmet feels good and another doesn’t. Some are rounder, others more oval.

If a helmet feels tight in one spot or leaves gaps in another, the shape may not match your head.

Can I use age to choose a bike helmet size?

No. Age isn’t a reliable way to pick a helmet. Kids of the same age can have very different head sizes, and even adults can vary. Always measure the head and use the helmet brand’s size chart to make sure it fits right.