Walk into almost any footwear department and one of the first questions you will hear is:
“What size are you?”
The customer answers, “I’m a nine,” and the fitter disappears into the stockroom.
But what exactly is a size nine?
It tells us surprisingly little about the foot we are trying to fit. It doesn’t tell us whether the customer has a broad forefoot or narrow heel, a high or low instep, whether one foot is larger than the other, where the ball of the foot sits, or how much the foot changes when body weight is applied.
And it certainly doesn’t tell us whether that particular foot corresponds with the three-dimensional shape around which the manufacturer designed the shoe.
Good footwear fitting isn’t about matching a number on a foot to a number on a box.
It is about matching the shape of a moving human foot to the shape of a shoe.
The Foot Is Not a Static Object
The human foot changes when it accepts body weight.
When sitting, the foot is relatively unloaded. When we stand, the structures of the foot accept our weight. The arch may lower, the foot can lengthen, the forefoot can broaden and its overall geometry can change.
That immediately exposes one of the limitations of taking only a single weight-bearing measurement.
A standing measurement tells us something about what the foot looks like under load.
It doesn’t tell us how much the foot changed when that load was applied.
For footwear fitting, that distinction can be extremely useful.
Pronation: More Than a “Fallen Arch”
Pronation is frequently described in footwear retail as having a “fallen arch”.
That is an oversimplification.
Pronation is a normal component of human movement. As the foot accepts load it becomes relatively flexible, allowing it to adapt to the surface beneath it and absorb forces.
The heel tends towards eversion and the medial longitudinal arch can lower. As this happens, the foot may become longer and broader.
Pronation is therefore not inherently a problem.
We all require it.
A person may also have a relatively low arch, or pes planus, without necessarily demonstrating problematic pronation. Foot posture and movement are related, but they are not the same thing.
For the footwear fitter, the important observation isn’t simply whether an arch appears low.
It is what happens to the dimensions of the foot when it becomes loaded.
Supination: Creating a Rigid Lever
Supination performs almost the opposite functional role.
The foot becomes relatively more rigid. The heel tends towards inversion and the arch becomes relatively higher, helping transform the foot from an adaptable structure into a stable lever for propulsion.
Again, supination is normal.
A persistently high-arched foot, or pes cavus, may have a more supinated and relatively rigid posture, but “high arch” and “supination” are not interchangeable diagnoses.
A useful simplification for footwear staff is:
PRONATION → flexibility → adaptation and load absorption
SUPINATION → rigidity → stability and propulsion
The question should therefore not be:
“Does this person pronate?”
Everybody does.
A better fitting question is:
“How does this person’s foot behave when it accepts load?”
Why Measure the Foot Twice?
A Brannock Device is a remarkably useful piece of equipment when used to gather information rather than simply produce a shoe size.
For a more complete fitting assessment, consider comparing the foot under two conditions.
Seated — relatively unloaded
With the customer sitting, place the foot consistently on the device in a neutral, relaxed position.
Measure both feet and record:
- heel-to-toe length;
- heel-to-ball length;
- ball width.
This provides a useful baseline measurement.
Standing — weight bearing
Now ask the customer to stand naturally and repeat the measurements.
Comparing the two can reveal how much the dimensions of the foot have changed under load.
For example:
| Measurement | Seated | Standing |
| Heel-to-toe | 8 | 8½ |
| Heel-to-ball | 8 | 9 |
| Ball width | D | EE |
Simply recording this customer as a size 8½ throws away most of the useful information.
The foot has demonstrated substantial dimensional change when loaded.
That may be highly relevant to the type of footwear and last that ultimately works for that customer.
It is important, however, not to turn this into amateur diagnosis. The difference between seated and standing measurements does not provide a clinical measurement of “how much somebody pronates”.
It demonstrates functional dimensional change under load. Pronation may contribute to that change, but it is not the only factor involved.
Heel-to-Ball: The Measurement We Too Often Forget
Heel-to-toe length receives most of the attention in footwear fitting.
But the heel-to-ball measurement can be just as important.
It tells us where the metatarsophalangeal region—the ball and natural forefoot flex area—sits in relation to the heel.
Imagine:
Heel-to-toe: size 8
Heel-to-ball: size 9
There might appear to be plenty of space in front of the customer’s toes in a size 8.
But the ball of their foot may sit too far forward in relation to the geometry and intended flex characteristics of that shoe.
This helps explain why a shoe can apparently be “the correct size” yet simply doesn’t feel right.
The end of the longest toe isn’t the only landmark that matters.
The Four Dimensions That Tell Us Much More
Once we move beyond simple length, several characteristics become particularly important.
Instep Height
Instep height is a major contributor to the volume of the foot.
Someone with a high instep can experience significant pressure beneath the tongue and laces even though the shoe appears perfectly adequate in length and forefoot width.
A customer with a low instep can have the opposite problem. They may have to pull the laces extremely tight simply to remove excess volume.
Increasing shoe size to solve high-instep pressure can therefore be counterproductive. It may create excessive length and alter the relationship between the foot and the rest of the shoe.
Ball Width
Ball width describes the breadth of the forefoot around the metatarsal heads.
It is important that this area corresponds reasonably with the broadest part of the footwear.
Too little space can compress the forefoot. Too much can allow unwanted movement.
But there is an important distinction:
Width is not volume.
A broad, shallow foot and a broad, high-volume foot may have similar ball widths while fitting completely differently inside the same shoe.
Heel Size
Heel width becomes particularly important in outdoor footwear.
A very common combination is:
broad forefoot + narrow heel.
Simply putting that customer into a generally wide shoe may solve the forefoot problem while creating significant heel movement.
Conversely, a narrow forefoot combined with a relatively broad heel presents a completely different fitting challenge.
Heel Depth
Heel depth and rearfoot volume determine how the calcaneus sits within the heel cup.
A shallow, low-volume heel inside a deep, high-volume heel cup may move excessively despite the shoe apparently being the correct length.
Heel width, heel depth and instep volume therefore need to be considered together.
What Volumental Adds
This is where 3D foot-scanning systems such as Volumental can considerably improve the information available to the fitter.
A conventional measurement primarily answers:
“How long and how wide is this foot?”
A 3D scan allows us to ask:
“What shape is this foot?”
Depending upon the system and measurements available, a 3D scan can provide detailed information about foot length, forefoot width, instep dimensions, heel and rearfoot characteristics, overall morphology and differences between the left and right feet.
Consider two customers who both conventionally measure as size nine.
One has:
wide forefoot + high instep + broad heel
The other has:
wide forefoot + low instep + narrow heel.
Calling both customers “a wide size nine” ignores a huge amount of relevant information.
They may require completely different lasts.
Left and Right Feet
Another major advantage of detailed measurement is that it highlights something experienced fitters have always known:
Feet are not necessarily symmetrical.
A customer may have:
Left: shorter, broader, higher volume.
Right: longer, narrower, lower volume.
Which one is the “size”?
There isn’t a useful single answer.
The footwear has to accommodate both feet.
The longest foot may determine minimum length while the broader or higher-volume foot creates an entirely different constraint.
Why a 3D Scan Doesn’t Replace the Fitter
Technology is useful, but it should support footwear fitting rather than replace it.
A weight-bearing 3D scan provides detailed information about the morphology of the loaded foot.
Comparing seated and standing measurements tells us something different:
how much the measurable dimensions changed when load was applied.
And neither tells us exactly what will happen once the customer puts on a particular shoe and starts walking.
The strongest approach therefore combines information:
Manual measurement + loaded/unloaded comparison + 3D morphology + experienced fitting + movement assessment.
Understanding the Last
To understand why all of this matters, we need to understand the last.
A last is the three-dimensional form around which a manufacturer designs and constructs footwear.
It isn’t simply a plastic model of an average naked foot.
The manufacturer designs it according to the intended customer, activity, materials and performance characteristics of the footwear.
Last design can take account of characteristics including:
- overall length;
- heel-to-ball relationship;
- ball width and girth;
- toe-box geometry;
- instep volume;
- heel width;
- heel depth;
- rearfoot volume.
The manufacturer then incorporates the allowances required for the intended use.
A technical climbing shoe needs a very different internal shape from a trekking boot.
An approach shoe may require precise heel retention and forefoot control.
A mountaineering boot needs to accommodate insulation, stiffness, climbing performance and potentially crampon compatibility.
A running shoe has another set of requirements entirely.
Consequently, two shoes labelled UK 9 can have markedly different internal shapes.
Neither is necessarily incorrectly sized.
They have been constructed around different lasts.
Why Going Up Half a Size Isn’t Simply Adding Toe Room
This is another important concept for footwear staff.
When a customer says:
“It’s tight across here.”
the almost automatic response can be:
“Let’s try half a size bigger.”
That may work—but understand what has been changed.
A larger shoe isn’t simply the same shoe with a few millimetres added beyond the toes.
Manufacturers grade their lasts through the size range. As size changes, multiple dimensions and anatomical relationships can change according to that grading system.
Increasing the size can therefore alter length, width, volume and the relationship between the customer’s foot and the geometry of the footwear.
The fitter may solve the original pressure problem while inadvertently creating excessive heel movement or placing the customer’s forefoot incorrectly within the shoe.
Sometimes the customer doesn’t need a bigger shoe.
They need a different last.
A Better Footwear-Fitting Process
A comprehensive outdoor-footwear assessment should therefore follow a logical progression:
Talk → Measure → Compare → Scan → Select → Fit → Move.
Start by asking what the customer intends to do in the footwear and what has or hasn’t worked previously.
Measure both feet relatively unloaded.
Repeat the measurements weight bearing and observe any dimensional change.
Use 3D scanning where available to understand foot shape, volume, instep and rearfoot characteristics.
Use that information to select footwear constructed around an appropriate last, rather than simply retrieving the customer’s usual size.
Once the footwear is on, assess:
- forefoot position;
- heel retention;
- instep pressure;
- overall volume;
- toe clearance;
- relationship of the ball of the foot to the shoe;
- comfort and security.
Finally, make the customer move.
Walk.
Climb an incline.
Descend.
A boot that feels wonderful while sitting on a fitting stool may behave completely differently when the customer walks downhill.
Measure, Don’t Diagnose
There is also an important professional boundary.
Outdoor-retail staff are footwear fitters, not podiatrists.
Measurement technology allows us to describe what we observe. It doesn’t automatically qualify us to diagnose pathology.
Instead of saying:
“You’ve got excessive pronation.”
it may be far more appropriate—and more useful—to say:
“Your foot becomes considerably longer and broader when you’re standing, so we need footwear that accommodates that change while still retaining your heel securely.”
The first statement is attempting a clinical diagnosis.
The second describes an objective fitting problem and proposes a footwear solution.
Customers presenting with persistent pain, neurological symptoms, significant deformity, injury or known pathology should be appropriately referred to a qualified healthcare professional rather than diagnosed on the shop floor.
Stop Selling Shoe Sizes
The customer’s statement:
“I’m a size nine.”
is useful.
But it is only the beginning.
The human foot has length, width, height, volume and shape. Its dimensions can change when loaded. The two feet can differ from each other. The position of the ball of the foot matters as well as the position of the toes.
The shoe also has length, width, height, volume and shape because it has been constructed around a particular last.
Good footwear fitting is the process of understanding the relationship between the two.
Think of it this way:
Unloaded measurement
What are the dimensions of the relatively unloaded foot?
↓
Loaded measurement
How do those dimensions change under body weight?
↓
3D scan
What is the detailed morphology and volume of each loaded foot?
↓
Last selection
Which footwear geometry best corresponds with those feet?
↓
Physical fitting
Does the foot actually fit the shoe rather than merely the size?
↓
Movement assessment
Does that relationship continue to work uphill, downhill and during walking?
Ultimately, the principle is remarkably simple:
The foot has a shape. The shoe has a shape. The last determines the shape of the shoe. Good footwear fitting is about matching those shapes.
The number printed on the box is merely where the process begins.
