How to Measure for a Dirt Bike Helmet? | Get the Right Fit

A dirt bike helmet that doesn’t fit won’t protect you properly, and it won’t be comfortable for long rides. The right fit starts with an accurate measurement, but it doesn’t end there. Different brands size their helmets differently, so the measurement is just the first step. Here’s how to get it right the first time, with no guesswork.

How To Take Your Head Measurement

You only need a flexible, non-stretchy tape measure—or a piece of string and a ruler if you don’t have one. Fox Racing recommends placing the tape around your head just above the eyebrows and ears, keeping it snug but not tight. Record the measurement in both inches and centimeters, as different brand charts may use either unit.

Bell Racing suggests a slightly different point: measure the circumference at a point approximately one inch above the eyebrows and at the back where it produces the largest possible measurement. Take several measurements and use the largest one, since that gives the most reliable result for helmet sizing.

The key is using a non-stretchy material. A soft cloth tape works, but a stretchy one or a piece of string that gives will throw the number off completely.

Match Your Measurement To The Right Size Chart

This is where most people go wrong. Your head measurement alone isn’t a size—it’s a number that has to be compared against the specific helmet brand’s chart. A 22-inch head might be a large in one brand and an extra-large in another. Fox Racing, Bell Helmets, and every other manufacturer calibrates their own sizing, so always use the chart for the exact helmet you’re considering.

If you plan to wear a balaclava or head sock while riding—and you should, for sweat management and comfort—measure and fit the helmet with it on. Bell Racing explicitly notes that wearing your under-helmet gear during fitting affects size selection.

Fit Check: Does It Actually Fit?

Once the helmet is on, the measurement is just a starting point. Fox Racing says the helmet should fit snugly around your head and cheeks without any pressure points or hotspots. Shake your head up and down and side to side—there should be minimal movement. If the helmet shifts significantly, it’s too large. If you feel pain or uncomfortable pressure, it’s likely too small or the wrong shape for your head.

Bell Helmets adds that the helmet should sit low enough to protect your forehead without hindering your vision. If it rides up, it’s not positioned correctly or the size is wrong. Many models allow you to adjust fit with replacement cheek pads or head liners in different thicknesses, so ask about those options before giving up on a model that’s close to the right size.

Our tested youth dirt bike helmet roundup has more details on specific models that fit young riders well.

Common Mistakes To Avoid

These errors are easy to make and hard to recover from if you’ve already bought the wrong size:

• Using a stretchy material for measuring—a flexible cloth tape or string that doesn’t stretch is the only reliable tool.
• Measuring too high or too low instead of around the widest part, just above your eyebrows and ears.
• Skipping the brand-specific size chart and relying on a generic guide.
• Ignoring the fit test—a helmet that moves or has pressure points is not properly fitted, regardless of the measurement.
• Fitting without your balaclava or head sock if you’ll wear one while riding.

Even a perfectly measured helmet won’t protect you if it moves around during a crash. The fit check is non-negotiable.