The shape of the skull plays an important role in the overall silhouette of the head. Apart from the jaw and the middle of the face, it mainly depends on the neurocranium: the frontal at the front, the parietals on the top and sides, the temporals laterally and the occipital at the back.
It is not enough to talk about a “big”, “small”, “wide” or “long” skull. Two people can have a comparable cranial volume and have very different shapes. You mainly have to look at its face width, its length from front to back, its height, the shape of the forehead and the way in which the volume is distributed between the front and the back.
To make consistent measurements, the head must remain in a neutral position. In profile, the Frankfurt plane is a good reference: the approximate line going from the top of the ear canal to the lower edge of the orbit should be horizontal. For photographs, it is better to move away from the camera and use a slight zoom rather than photograph the face up close with a wide angle.
1. General proportions of the skull
a. Width and length
The first measurement allows you to know if the skull is rather long and narrow or short and wide. This is the cephalic index.
The maximum length of the skull is measured from the glabella to the opisthocranion. The glabella corresponds to the central point located between the eyebrows, slightly above the root of the nose. The opisthocranion corresponds to the point on the back of the skull that protrudes the most. You must measure the distance in a straight line between these two points and not follow the curvature of the scalp. The classic anthropometric measurement is done with a thickness caliper.
The maximum width is measured between the two euryons. These are not easily visible fixed points: the euryons simply correspond to the most lateral points on each side of the skull. They are generally located in the parietal region, above the ears. In practice, we move the compass slightly around this area until the maximum width is found.
The cephalic index is calculated as follows:
maximum width ÷ maximum length × 100
For example, a skull with a width of 153 mm and a length of 197 mm has an index of 77.7.
Traditionally, an index lower than around 75 corresponds to a dolichocephalic shape, therefore long and narrow. Between about 75 and 80, the skull is mesocephalic. Above 80, it becomes brachycephalic, therefore relatively short and wide.
For male aesthetics, the 75 to 80 zone is a good general benchmark if you are looking for an intermediate or slightly elongated shape. Around 77 to 79, the skull generally has a significant depth without becoming particularly narrow.
However, this index should not be interpreted alone. It doesn't say where the length of the skull is. A long head with a large occiput does not have the same shape as a head of the same length with more depth at the front.
b. Height of the neurocranium
Height should be measured independently of width and length.
A relatively simple measurement is the tragion-vertex distance. The tragion is located in front of the opening of the ear, at the level of the small cartilaginous relief of the tragus. The vertex is the highest point of the head when held straight.
You should not place a meter on the curvature of the head. The vertical height is measured between the level of the tragion and the top of the skull.
The ratio can be calculated as follows:
tragion-vertex height ÷ maximum skull width
In adult men, a ratio around 0.80 to 0.86 constitutes a common order of magnitude, with around 0.83 as a central value.
A significantly higher ratio results in a relatively tall and narrow neurocranium. A lower ratio results in a lower, wider silhouette.
This measurement should not be confused with forehead height. A high hairline can produce a large forehead without the skull being particularly high.
2. The skull seen from the front
a. Width of the skull in relation to the face
From the front, the first characteristic to look at is the width of the neurocranium in relation to the face.
For this we use the euryon-euryon width described previously. It is compared to the bizygomatic width, that is to say the distance between the two most lateral points of the cheekbones.
To measure the latter, you must look with your fingers for the place where each zygomatic arch protrudes the most, then measure in a straight line from one side to the other.
The ratio is:
skull width ÷ bizygomatic width
In large anthropometric male samples, the width of the skull is generally slightly greater than that of the cheekbones. A ratio of around 1.05 to 1.10 therefore constitutes a consistent area.
At 1.00, the cheekbones and skull are almost the same width. Around 1.05 to 1.10, the neurocranium extends slightly beyond the face. Beyond approximately 1.10 to 1.12, the upper part of the head becomes particularly wide in relation to the cheekbones.
This measurement is more useful than absolute width. A 155mm head is not particularly wide if the face itself is 147mm, whereas it will appear wider on a 135mm face.
b. Width of forehead and temples
The forehead should be distinguished from the maximum width of the skull.
The measurement used is the minimum frontal width, or frontotemporal-frontotemporal distance. You should look on each side of the forehead for the place where the temples tighten the most, approximately above and slightly outside the eyebrows.
We can then compare this measurement to the maximum width of the skull:
frontotemporal width ÷ skull width
A ratio around 0.68 to 0.72 gives a forehead significantly narrower than the parietals without creating extreme tightness.
It can also be compared to the width of the cheekbones:
frontotemporal width ÷ bizygomatic width
A ratio of around 0.72 to 0.76 is a consistent order of magnitude.
A much higher ratio produces a fairly uniform top in width. A significantly lower ratio, on the contrary, produces narrow temples with significant widening of the parietals above.
However, the shape of the forehead also depends on its geometry. A rather square forehead has relatively straight or slightly converging sides, while a very rounded forehead joins the sides of the skull more gradually.
c. Shape of the parietals and vertex
The maximum width of the skull is generally located at the level of the parietals. Their shape largely determines the upper contour of the head.
When the parietals protrude strongly above narrow temples, the head can take on a bulb shape. When the sides rise more gradually towards the top, the silhouette appears more regular.
The top of the skull should also be observed separately. A balanced contour gradually rises from the sides then forms a smooth curve around the vertex.
A very narrow top gives a more pointed or pointed shape. A very flat top combined with vertical sides produces a more rectangular shape.
There is no simple ratio useful enough to measure this curvature. A precise analysis would require several cross-sectional measurements or a 3D scan. In a frontal photograph, the general outline therefore remains more informative than an isolated number.
3. The forehead seen in profile
a. Frontal projection
The profile allows you to see not only the height of the forehead, but also its position from front to back.
A projected browband places more bone structure in front of the ear. The supra-orbital arches, the forehead and the rest of the face then seem to belong more to the same advanced construction.
Conversely, when the frontal part moves quickly backwards, a greater part of the cranial volume appears to be located behind the face.
This is what is often called a “forward grown” front. The term has no official anatomical definition, but it describes a significant anterior depth of the skull quite well.
This projection does not have a simple and universal ratio. It is best assessed with the total anterior depth of the skull, described later with the relationship between nasion, tragus and occiput.
b. Forehead tilt
Tilt can be measured quite easily in a profile photograph.
We locate the glabella, located between the eyebrows, then the trichion, that is to say the point where the median line of the forehead meets the hairline. We draw a line between these two points, then we compare this line to the vertical when the head is positioned in the Frankfurt plane.
A perfectly vertical front corresponds to approximately 0° of recoil. The further back the top of the forehead, the more the angle increases.
Values vary depending on the exact method of measurement. For a simple aesthetic analysis, approximately 5 to 15° corresponds to a relatively straight to moderately inclined forehead. Around 15 to 20°, the slope becomes more visible. Beyond that, the front seems frankly elusive.
Slope should not be judged alone. A projected supra-orbital arch with a moderately inclined brow does not produce the same profile as a fully recessed entire brow.
c. Glabella and supra-orbital arches
The glabella is the central protruding point between the eyebrows. The supraorbital arches extend laterally above the eyes.
In men, these structures are on average more marked and are part of the areas of the frontal part presenting the most sexual dimorphism.
Sufficient projection gives greater relief to the transition between the eyes and the forehead and visually increases the depth of the orbits.
It is difficult to express this characteristic with a simple ratio without 3D imaging. On a profile photograph, however, we can draw a vertical line passing through the upper part of the forehead and then look at how much the glabella protrudes forward.
The interest remains mainly qualitative: a glabella slightly advanced in relation to the frontal produces a visible supra-orbital relief. A glabella nearly aligned with the forehead produces a smoother surface.
4. The depth of the skull seen in profile
a. Anterior depth and front/back ratio
One of the most important elements of the profile is the amount of head in front of the ear relative to the overall depth.
To measure it, we use three landmarks: the nasion, the tragus and the back of the skull.
The nasion corresponds to the root of the nose, at the junction between the frontal and the nasal bones. In a photograph, it is located approximately in the hollow between the eyes and the top of the nose.
The tragus is the small relief located in front of the ear canal.
The last point is the most posterior point of the occiput.
We then measure:
nasion → tragus
then:
nasion → occiput
The ratio is:
nasion-tragus ÷ nasion-occiput × 100
For example, if the nasion-tragus distance measures 110 pixels and the nasion-occiput distance measures 190 pixels:
110 ÷ 190 × 100 = 57.9%
An area of around 55-60% is the main benchmark used, with around 57-59% as the central value.
Around 50%, the ear is closer to the middle of the total depth. The lower the ratio goes, the more of the head is located behind the ear. Conversely, a ratio greater than 60% indicates a particularly significant anterior depth.
This ratio is much more useful than just overall head length. Two people can have exactly the same cranial depth but very different front/back distribution.
You must use a strict profile. A slight rotation of the head visually moves the tragus and occiput and can distort the measurement.
b. Posterior part and occiput
The occiput forms the back of the skull. It can be relatively flat or have a more developed curvature.
To assess its length, we can simply measure the horizontal distance between the tragus and the most posterior point of the skull.
This measurement taken alone, however, provides little information. A developed occiput is not necessarily unfavorable if the skull also has a lot of depth at the front.
The front/back ratio therefore remains more interesting.
With an anterior ratio of 55-60%, the portion behind the tragus level roughly represents the remaining 40-45% of the overall depth.
The problem appears especially when the occiput constitutes a large part of the total depth while the frontal and anterior region are short. The head then appears more developed towards the rear.
A slightly rounded occiput can, on the contrary, fit normally into a profile with good anterior depth.
5. The cranial vault
a. Curvature position
The arch corresponds to the transition between the forehead and the top of the skull.
A “high-set cranial vault” does not simply mean that the head is high. Above all, this means that the front maintains its upward direction for a relatively long distance before starting to curve backwards.
Conversely, with a low arch, this curvature begins much earlier. A significant part of the top of the forehead then already belongs to the upper curve of the skull.
The best way to observe it is to use a strict profile and locate the point where the forehead line begins to change direction significantly towards the rear.
The higher this point is, near the hairline or the top of the frontal, the higher the arch can be described as. When it is significantly lower on the forehead, it appears lower.
There is no standard ratio sufficiently established to justify a precise value. This characteristic is therefore better described by the relative position of the curvature than by an arbitrary number.
b. Arch length
We must distinguish the point where the arch begins from the length of the curve which then leads to the top and back of the skull.
A short arch produces a relatively compact top. A very long arch further extends the curvature across the entire upper part of the head.
An often sought-after combination is a curvature that starts quite high but remains relatively short. The frontal thus retains a significant anterior surface before reaching the summit, without the entire upper part of the skull stretching backwards.
As with its position, this length is mainly assessed visually. An accurate measurement would require following several points on the curve of the skull rather than measuring a simple straight distance.
6. The general form sought
a. From the front
From the front, the desired silhouette generally has a neurocranium slightly wider than the cheekbones, without the parietals becoming disproportionate.
A skull width/bizygomatic width ratio of around 1.05 to 1.10 constitutes a good benchmark.
The forehead is narrower than the maximum width of the skull, with a frontotemporal/cranial width ratio around 0.68 to 0.72. The temples are neither excessively wide nor strongly constricted.
The apex forms a regular curve and the height remains proportional to the width, with a tragion-vertex/skull width ratio around 0.80 to 0.86.
b. In profile
In profile, the anterior depth constitutes a central element.
A nasion-tragus / nasion-occiput ratio around 55 to 60%, particularly around 57 to 59%, corresponds to a significant part of the depth placed in front of the level of the ear.
The frontal remains relatively projected and its slope is low to moderate. An approximate inclination of 5 to 15° from the vertical corresponds to a relatively straight front, while a slope greater than 15 or 20° becomes much more visible.
The glabella and the supra-orbital arches create relief at the base of the forehead. The curvature of the arch begins relatively high and the occiput does not represent an excessive proportion of the total depth.
c. The “warrior skull”
The warrior skull can ultimately be understood as a combination of these different characteristics rather than as a distinct anatomical type.
From the front, it generally presents a skull slightly wider than the cheekbones, a structured forehead, temples narrowed enough to distinguish the frontal from the parietals and a moderate height.
In the horizontal plane, a cephalic index around 75 to 80, often around 77 to 79, gives an intermediate or slightly elongated shape.
In profile, the frontal has sufficient depth, the supra-orbital arches are visible, the forehead does not recede strongly towards the rear and a significant proportion of the head is in front of the ear. A front/back ratio of around 55 to 60% sums up this characteristic quite well.
The occiput may be slightly rounded. The main point is that it does not concentrate a large part of the length of the head on its own.
7. Measures to remember
a. Cephalic index
Measurement: maximum euryon-euryon width ÷ glabella-opisthocranion length × 100
Benchmarks:
less than 75: rather long and narrow skull
75 to 80: intermediate skull
over 80: rather short and broad skull
Aesthetic reference zone: approximately 77 to 79.
b. Width of the skull in relation to the cheekbones
Measurement: euryon-euryon width ÷ zygion-zygion width
Benchmark: approximately 1.05 to 1.10.
The skull is therefore approximately 5 to 10% wider than the cheekbones.
c. Forehead width
Measurement: frontotemporal width ÷ maximum skull width
Benchmark: approximately 0.68 to 0.72.
In relation to the cheekbones: frontotemporal width ÷ bizygomatic width
Benchmark: approximately 0.72 to 0.76.
d. Height of the neurocranium
Measurement: tragion-vertex height ÷ maximum width of the skull
Benchmark: approximately 0.80 to 0.86.
Central value: approximately 0.83.
e. Forehead tilt
Measurement: angle between the glabella-trichion line and the vertical, head positioned in the Frankfurt plane.
Benchmark: approximately 5 to 15° for a slight to moderate slope.
Beyond 15 to 20°, the retreat of the front becomes more marked.
f. Front/back ratio
Measurement: nasion-tragus distance ÷ nasion-occiput distance × 100
Benchmark: approximately 55 to 60%.
Useful central value: approximately 57 to 59%.
Among all these measurements, the four most informative are the cephalic index, the ratio between skull width and cheekbone width, the relative height of the neurocranium and the front/back ratio. They already make it possible to describe a large part of the general shape of the skull.
