How to Measure Head Size for a Motorcycle Helmet

To measure head size for a motorcycle helmet, wrap a soft tape measure around the head about one finger width above the eyebrows and across the widest part at the back, then read the number in centimeters or inches. Compare that figure with the sizing chart for the exact model, because the letter sizes are not standard across brands. This guide covers the tools you need, the steps, a worked example, how head shape changes the answer, and the in-person checks that confirm a helmet really fits.

What you need before you start

The job takes about five minutes and needs very little equipment. A flexible tailor’s tape is the best choice because it follows the curve of the head. If you only have a rigid metal tape, a piece of string and a ruler will do the same job. A mirror helps you keep the tape level, and a second person makes the measurement more accurate.

• A soft sewing tape or a length of non-stretch string
• A ruler or rigid tape measure if you are using string
• A pen and paper to record each reading
• A mirror, or a friend to check that the tape stays level

Measure with dry, flat hair and no hat. Thick hair styles, bulky hair ties or a ponytail at the back can add noticeable length to the reading, so remove them or flatten them first.

Step-by-step: measuring head circumference

1. Stand in front of a mirror and hold the zero end of the tape against the center of the forehead, about a finger width above the eyebrows.
2. Wrap the tape around the head above the ears, keeping it level at the front and back. Run it across the fullest part at the back of the skull, which is usually just above the bump at the base of the skull.
3. Bring the tape back to the front and read where the end meets the zero point.
4. Keep it snug without pressing into the skin. It should not dig in, and it should not hang loose.
5. Write down the reading, then remove the tape and repeat the process two more times.
6. Use the largest consistent reading, or average the three if they are within a few millimeters.

Do not trust a single attempt. Tape that drifts upward at the back or sags over one ear can shift the number by more than a centimeter, and that is enough to move you into another size.

A worked example with stated assumptions

Suppose a tape reads 22.6 inches. Multiply by 2.54 and the result is 57.4 centimeters. Assume the model you are considering lists medium as 57 to 58 centimeters, large as 59 to 60 centimeters and small as 55 to 56 centimeters. Your reading sits in the middle of the medium band, so medium is the logical first try.

Now change the assumption. If the chart for another model lists medium as 56 to 57 centimeters and large as 58 to 59 centimeters, the same head sits between the two. That is where the second layer of fitting comes in. You would try the medium with the thickest cheek pads on offer, check the pressure points, and only move up if the helmet creates a headache or leaves a visible mark on the forehead.

Common conversion ranges and how to read a chart

The table below shows a pattern many brands use. It is a general illustration only, so check the manufacturer’s current chart for the model you plan to buy.

Check whether the chart uses centimeters or inches, and whether the ranges overlap. Some brands include separate sizing for each shell, and some list a tolerance of half a centimeter on either side. When a number lands on a boundary, read the notes under the chart, because that is where manufacturers explain how to choose.

Head shape matters as much as size

Two people with the same circumference can need different helmets. Head shape is usually described as round oval, intermediate oval or long oval. A round oval head is almost as wide as it is long from front to back. A long oval head is narrower from side to side and longer from front to back. Intermediate oval sits in the middle and fits most helmets built for general use.

A quick check: look down at your head from above in a photo, or ask someone to stand behind you. If the outline looks close to a circle, it is round. If it looks like a stretched egg, it is long. A mismatch tends to show up as pressure on the forehead or temples, with gaps at the sides. Many makers publish which shape each model is intended for, so match that detail to the shape you have.

Checking the fit in person

The tape is a starting point. The true test is how the helmet sits when it is on and fastened. Put the helmet on slowly, spreading the strap ends apart to widen the opening, and then fasten the retention system. Wear it for at least 20 to 30 minutes at home, looking for patterns rather than momentary tightness.

• Cheeks. Firm, even contact, with the face skin moving when you move your jaw.
• Forehead. No gap you can slip a finger into, and no sharp pressure line.
• Shake test. With the strap fastened, move the helmet side to side and up and down. The skin should move with it rather than the helmet sliding over the skin.
• Roll-off check. Fasten the strap, tilt your head forward and have someone try to roll the helmet off from the back. It should stay in place.
• Eyes and glasses. The eye port should sit evenly in front of the eyes, and any glasses should slide in without strong pressure at the temples.
• Chin strap. You should be able to fit about two fingers under it when fastened, and it should not slip off the chin.

Mistakes that lead to the wrong size

The most frequent error is measuring too low, around the ears and neck, which gives a bigger number than the helmet’s reference point. Another is pulling the tape too tight, or leaving it loose because the hair gets in the way. A third is guessing from the size of a hat or a bicycle helmet. These are made for different shapes and are rarely a reliable guide to motorcycle helmet size.

A fourth mistake is choosing a larger helmet for comfort. A shell that is too big moves on impact, increases wind noise and can shift down over the eyes. Finally, buying based on the size of an older helmet is risky when padding has worn flat. The old helmet may now feel too roomy, which can make a new correctly sized one seem tight at first.

When to ask for professional help

If measurements fall between sizes, or you have a very long or very round head, a visit to a motorcycle gear shop is worth the time. A trained fitter can compare shell shapes, swap cheek pads and spot pressure points that you might not notice. If a helmet leaves numbness, persistent headaches or marks that last more than a few minutes, take it off and talk to the retailer. Safety standards apply to the helmet as designed, so a poor fit can undo the protection.

Related guides

• Full Face Motorcycle Helmet For Small Heads
• Quiet Motorcycle Helmets For Highway Riding
• Dual Sport Helmets For Adventure Riding

Frequently asked questions

Which measurement matters most for helmet sizing?

The circumference of the head, taken about one finger width above the eyebrows and around the fullest part at the back, is the number that drives sizing. Brands convert that figure to S, M or L using their own charts. Head shape and cheek width also change how a given size feels, so treat the tape reading as a starting point, not the final answer.

What if the measurement falls between two sizes?

Check the manufacturer chart first, since some brands sell intermediate shells or extra cheek pad thicknesses. If you are still between sizes, many fitters suggest starting with the smaller one, because padding compresses over the first weeks of riding. Do not go smaller than you can comfortably wear for 30 minutes, and avoid buying a size that creates a hot spot.

Should a new helmet feel tight?

It should feel snug and even, with firm contact around the whole head and cheeks pressing gently on the face. It should not cause sharp pain, headaches or pressure points on the forehead. Some tightness is normal because padding breaks in, but if you see red marks or numbness after a short wear, the shape or the size is probably wrong.

Can a piece of string replace a tape measure?

Yes. Wrap the string around the head at the same height you would place a tape, mark the point where it overlaps, then lay the string flat against a ruler or hard tape measure. Keep the string taut but not squeezing, and repeat the measurement a few times. A flexible sewing tape is easier, but string works well when nothing else is at hand.

Do helmet sizes vary between brands?

Yes. A medium from one maker can feel different from a medium from another because of internal shape, padding thickness and liner design. Sizing charts in centimeters or inches are a useful guide, but shell size, head shape fit and cheek pad options differ. Always read the specific chart for the model and, where possible, try the helmet on before committing.