How to Measure Your Mountain Bike Helmet Size Accurately

Getting Your Mountain Bike Helmet to Fit Right

Measuring your head for a mountain bike helmet is the most important step you can take. A poorly fitting helmet can be dangerous. It might shift during a crash or not cover vital areas of your head. We found that most riders get this right by following a simple process.

What You’ll Need for an Accurate Measurement

Before you grab any old measuring tape, let’s talk about what works best. A flexible tape measure is your best friend here. Think of the kind you might use for sewing or tailoring. A metal tape measure can be too stiff. It won’t bend to the curves of your head. You want something that can accurately contour your head shape.

If you don’t have a flexible tape measure, don’t worry! You can use a piece of string or a shoelace. Just mark the length that fits your head. Then, lay the string flat against a standard ruler or tape measure to get your measurement. This method works just as well for a snug fit.

How to Take the Measurement: Step-by-Step

This is where we get down to business. Getting this measurement right is key to finding a helmet that feels like it was made just for you. Ready?

Finding the Right Spot on Your Head

You don’t want to measure right at your hairline. This can lead to a helmet that feels too tight. The sweet spot is usually about an inch (or two fingers’ width) above your eyebrows. This is where most helmets sit.

Imagine your helmet sitting on your head. Where is the front edge going to be? That’s the general area you want to measure around. We found that measuring slightly higher than you might first think often leads to the best helmet fit. It ensures the helmet sits low enough for proper protection.

Wrapping the Tape Measure

Now, take your flexible tape measure. Wrap it around your head. Make sure it goes around the widest part of your head. This is typically just above your ears and over the fullest part of your forehead. Keep the tape measure level and snug, but not too tight. You don’t want to be squishing your head!

This is similar to how you’d measure for a hat. The goal is to get a measurement that represents the actual circumference of your head where the helmet will rest. Many experts recommend taking this measurement a couple of times to ensure accuracy. It’s a small step that makes a big difference.

Reading and Recording Your Measurement

Once the tape measure is in place, note the number where the tape overlaps. It’s a good idea to write this down in both inches and centimeters. Helmet brands often use both units in their sizing charts. Having both numbers ready saves you time later.

Don’t round up or down too much. The more precise you are, the better. If you used a string, now is the time to measure its length against a ruler. We found that a difference of even half an inch can sometimes put you between sizes.

Understanding Helmet Sizing Charts

Now that you have your head measurement, it’s time to compare it. Every helmet brand has its own sizing chart. These charts are usually found on the brand’s website or on the helmet’s packaging. They list different helmet sizes (like Small, Medium, Large, or numbers like 55-59 cm).

Look for the range that your head circumference falls into. For example, if your head measures 22.5 inches (57 cm), and a brand’s Medium size is 56-58 cm, then Medium is likely your size. If you fall exactly on the border between two sizes, what should you do?

What to Do If You’re Between Sizes

This is a common situation, and we’ve seen many riders puzzled by it. Often, it’s best to try on both sizes if possible. If trying on isn’t an option, consider the helmet’s padding. Some helmets come with thicker or thinner padding inserts. You might be able to adjust the fit slightly with these.

Generally, if you’re on the smaller end of a size range, you might lean towards the larger size with thicker padding. If you’re on the larger end, the smaller size with thinner padding could work. However, a helmet that is too large is never a good idea. It won’t offer adequate protection.

The Importance of a Snug Fit

Why is all this measuring so important? It comes down to safety and comfort. A helmet needs to stay put, especially in a fall. If it’s too loose, it can rotate or even come off your head during an impact. This defeats its purpose entirely.

A helmet that’s too tight can cause headaches and discomfort on longer rides. You won’t want to wear it, which is also a safety issue. You want a helmet that feels snug and secure, almost like a second skin, without pinching or causing pain. Many helmet manufacturers suggest that a proper fit should feel snug from the moment you put it on, with no significant gaps.

A Quick Checklist for Your Measurement

• Grab a flexible tape measure.
• Measure about one inch above your eyebrows.
• Ensure the tape is level and snug around your head.
• Record the measurement in inches and centimeters.
• Compare your measurement to brand-specific sizing charts.
• If between sizes, consider trying both or looking at padding options.

Example Helmet Sizing (Brand Varies)

Size	Circumference (cm)	Circumference (in)
Small	51 – 55 cm	20 – 21.7 in
Medium	55 – 59 cm	21.7 – 23.2 in
Large	59 – 63 cm	23.2 – 24.8 in

This table is just an example. Always check the specific sizing chart for the brand you are interested in. We found that sizes can vary quite a bit between different manufacturers.