Determine your head shape for a motorcycle helmet: guide with head index

Almost every motorcyclist knows their helmet size, but very few are familiar with their own head shape - which quickly turns buying a helmet into a guessing game. Your head circumference tells you whether to reach for an M or an L, but whether the inner shell actually fits your skull isn't printed on any label. Two heads with an identical circumference of 57.5 centimetres can look completely different from above - one like a rugby ball, the other more like a football - and a lid that fits one will press on the other's forehead while leaving gaps at the sides. In this guide and in our motorcycle helmet new releases video from EICMA, we show you how to determine your head shape with simple tools and what the resulting number means for your next helmet.

To make this as practical as possible, we measured 13 heads from the 1000PS editorial team with a tape measure and calipers and compared the results with 24 new helmets for 2027 that NoPain tried on himself at EICMA 2026 in Milan. You'll find out further down which models tend to suit long, intermediate oval or rounder heads. But first, we'll show you how to take the necessary measurements yourself.

For your head circumference, all you need is a flexible tape measure, the kind you should find in any sewing kit. Wrap it horizontally around your head, one to two centimetres above your eyebrows at the front and, at the back, over the point where the back of your head protrudes the most. The tape should sit snugly without digging in, and since just a few millimetres often decide between two sizes, it's worth measuring three times and taking the largest value. We keep coming across two mistakes: either the tape is pulled up at an angle at the back, or it sits too high at the front and slips off the back of the head. In both cases you miss the widest point, and the size you derive from it will be wrong.

NoPain comes in at 57.5 centimetres, which puts him in size M with practically every manufacturer. If you're right between two sizes, try on both, because at this point at the latest your head shape has a say too - and that's what the next two steps are about. Everything else about choosing a size, from the size chart to the correct fit, can be found in this helmet size guide.

For your head shape you need two more measurements: the length and the width of your head. The length runs from your forehead between the eyebrows to the rearmost point of the back of your head; the width is measured at the widest part of the skull, roughly two fingers above the ears. We used calipers for this, i.e. a large compass with curved arms whose tips rest against both points, with the distance then read off a ruler. From these two values you calculate your head index by dividing the width by the length and multiplying the result by 100. For NoPain that's 15.2 centimetres wide and 20.0 centimetres long, giving an index of exactly 76.0.

How to measure length and width at home without calipers The principle: for the width, your helper holds two books parallel against the left and right side of your head, roughly two fingers above the ears, and measures the distance between the covers. For the length, lean the back of your head against a wall while your helper holds a book flat against your forehead just above the eyebrows. Then measure from the wall to the book.

Press thick hair flat while doing this, otherwise you're measuring your hairstyle instead of your skull, and take each measurement two or three times. If the values differ, use the average. One millimetre shifts the index by around half a point, which only matters if you're right at a boundary. After a few minutes you'll have two numbers that tell you more about your next helmet purchase than any size label.

The lower your head index, the longer your head is in relation to its width. Up to 75.9 is called a long oval head, which from above resembles a rugby ball. Between 76.0 and 80.9 lies the intermediate oval shape, for which the majority of helmets are built, and from 81.0 upwards begins the round oval head, where length and width differ only slightly. The classification comes from anthropology (Martin/Saller, 1957) and applies to adult men; for women the boundaries are around one point higher. Helmet manufacturers talk about Long Oval, Intermediate Oval and Round Oval; however, there's no binding scale in the industry defining from which value a helmet counts as long oval. That's why we don't rely on manufacturer claims but put every helmet on ourselves.

At 76.0, NoPain is just about intermediate oval, but already has one foot in the rugby camp. A helmet built for round heads therefore makes itself known after a few minutes with a pressure point on his forehead.

Our small sample from the editorial team alone shows how different heads are. Of the 13 heads measured, three are long oval and ten intermediate oval; we didn't find a round oval one. Between the longest head, Mex at 70.6, and the roundest, Philipp at 80.2, lie almost ten index points, even though the head circumferences differ by only a few centimetres. Alongside Mex, McGregor at 74.2 and Nastynils at 75.8 count among our long heads, NoPain sits right on the boundary at 76.0 and cameraman Schaaf just behind at 76.4. It's not representative, but it does show that almost one in four of us falls outside the standard shape most helmets are built for.

A look at the favourite helmets of our long heads is revealing: all three swear by Arai and Shoei, and Mex has also had good experiences with HJC. Still, you shouldn't blindly trust the brand, because as our fittings at EICMA showed, the internal shape often varies from model to model within the same manufacturer.

One question we hear again and again: can't a helmet that presses on the forehead or temples simply be made to fit with different pads? Sometimes yes, but unfortunately mostly not. Most premium manufacturers do offer cheek and crown pads in various thicknesses, and Shoei even has its own inserts that change the internal width of the helmet. At the forehead and top of the head, however, your skull usually sits directly against the EPS inner shell, i.e. the polystyrene, and there's nothing to swap there. If a helmet is clearly shaped one way and your head the other, even the thickest pad set won't help - you'll need a different model.

Then there are the shell size jumps. Many helmets are offered in six or seven sizes but made with only three or four outer shells, so several sizes share one shell and the right internal circumference is only achieved via the EPS and pad thickness. HJC gave us an example of this at EICMA: the RPHA 71 had four outer shells, while the RPHA 72 makes do with three. So if you fitted perfectly in an M in the old model, you can't rely on an M fitting in its successor too. Simply buying one size up isn't a solution either, because a helmet that's too big shifts around, gets louder and protects less well - you'll notice it at motorway speeds or after two hours in the twisties at the latest.

The head index doesn't replace trying a helmet on, but it saves you a lot of fittings, because you already know beforehand which helmets you don't even need to put on and what to look out for during the test fit. Put the helmet on, close the chin strap and keep it on for at least ten minutes, even if it gets tedious in the shop - after all, you'll wear it for longer on a day tour through the twisty roads. Turn your head, nod and pay attention to where pressure builds up. If a red mark remains on your forehead afterwards, the helmet is too round for your head; if it presses on your temples, it's too long. Glasses wearers should definitely bring their everyday glasses to the fitting, because whether the arms fit behind the ears without pressure only becomes clear with the helmet on.

At EICMA 2026, NoPain tried on the most important 2027 helmet releases, each in size M, and classified them with his head index of 76.0. For the glasses test he brought the same reference glasses with extremely slim arms to every stand, which represents the best-case scenario - if your arms are wider, expect a bit less room. The classification is based on a single head and a few minutes at the trade show stand, so it's no substitute for a long-term test. But you can translate it to your own situation with your own index: if your value is well below 76, a tip for longer heads applies to you all the more; if it's well above 78, the same goes for the tip for rounder heads.

If you have a long head, you should take a closer look above all at the Arai Horizon-X, the new Shoei NXR3 and GT-Air 3 Smart, and the HJC F72 and i101; off-road, the Bell Moto-10 GP and the Suomy MR Jump 2.0 join the list. For rounder heads, it's worth trying on the Shark Skwal iCup, the KYT NM-1, the LS2 models New Ranger and Valiant Gear, and Sena's Phantom Camera and Specter KV. NoPain shows all the new releases with prices, tech and the interviews from the show stands in the walkaround video.

If you know your head index, you'll save yourself most of the fittings next time you buy a helmet and will know immediately with every pressure point whether a different pad will help or whether the model simply doesn't suit your head. If your value sits in the middle of the intermediate oval range, you have the widest choice, because most helmets are built precisely for that middle ground. If, on the other hand, you're long oval like three of our 13 colleagues, or round oval, measuring is especially worthwhile, because part of the range is ruled out from the start. A tape measure and books don't replace a fitting, but they make sure you put on the right helmets straight away.