The Orthotic Volume Rating: Does Your Shoe Actually Have Room for Your Orthotic?
How much room a shoe really has once the stock insole comes out and an orthotic goes in. Our 1 to 5 rating, plus a 60-second check you can do in the store.
Written and medically reviewed by Dr. Tom Biernacki, DPM, FACFAS · Last reviewed 13 September 2026
On this page
Testing status: the Orthotic Volume Rating is a clinical rubric, not a lab measurement. Ratings published across this site are scored by hand — a device placed in the shoe, the heel checked inside the counter, the same way it is done chairside. Bench measurements of interior volume are in progress and are not published yet. We do not print a figure we have not measured.
The short answer
The Orthotic Volume Rating is a 1 to 5 score for how much interior room a shoe still has once you pull the stock insole out and drop an orthotic in. A 5 means the device disappears into the shoe and your heel still sits down inside the heel counter, where it belongs. A 1 means the device raises your foot so far that the heel rides at the top of the counter or above it — the collar starts rubbing, the heel slips with every step, and the shoe you bought for stability has become the least stable part of the setup.
It exists because the most common reason a perfectly good orthotic fails is that it was put in the wrong shoe.
Why the shoe decides the fit, not the device
An orthotic is a fixed object. Once it is made — cast from your foot or pulled off a rack — the thickness under the heel, the height of the arch and the width of the shell do not change. What changes from shoe to shoe is the space available to hold it.
That space was decided by the brand long before you tried the shoe on: how deep the last is through the heel and midfoot, whether the upper is lasted to a board or to a fabric strobel, how tall the heel counter stands, how much material the stock insole was occupying, and how much lacing range is left to take up slack across the instep. Two shoes in the same size, from the same brand, in the same year, can differ enormously on all five.
So when someone tells me their orthotics hurt, the first thing I ask to see is the shoe. More often than not the device is fine and the shoe never had the volume to hold it.
What the rating looks at
- Whether the stock insole comes out at all, and how much material leaves with it. A thick moulded footbed that is glued down is volume you cannot reclaim.
- Heel pocket depth — how far down into the shoe the heel can still sit once a device is underneath it.
- Heel counter height relative to the raised foot. This is the failure that matters most. The rim of the counter should stay above the widest part of your heel, not cut across it.
- Midfoot and instep volume, and whether the lacing has enough range left to hold the foot down against a device that has lifted it.
- Forefoot height, which matters for devices carrying a metatarsal pad or a thicker top cover.
What it is not: the rating is not a comfort score, not a durability score, and not a brand claim repeated back to you. A shoe can rate a 5 for volume and still be the wrong shoe for you for a dozen other reasons.
The 1 to 5 scale
- 5 — Generous. Removable insole, deep heel pocket, tall counter. A full-length custom device drops in and the heel sits down as though the shoe were built for it. Purpose-built walking shoes on a depth last usually land here.
- 4 — Comfortable. The device fits with room to spare. You may want a half size longer once the arch takes up space, but nothing is fighting.
- 3 — Workable with a trim. The shell fits after the top cover is shortened, or if the device is ordered three-quarter length. A lot of mainstream running shoes sit here.
- 2 — Tight. The heel rides high enough that the counter no longer sits where it should. A low-profile prefabricated insole may work; a full custom device usually will not.
- 1 — No room. Glued-in footbed, shallow last, low collar. Adding a device makes this shoe worse than it was empty.
How to check a shoe yourself, in about a minute
- Take the stock insole out. If it will not come out, you already have your answer for most devices.
- Put your orthotic in flat against the bottom of the shoe, heel pushed all the way back. It should lie flat, with no rocking and no curling at the edges.
- Put the shoe on and lace it properly. Do not skip this — an unlaced shoe always feels worse than it is.
- Stand up, and find the top of the heel counter with your thumb: the firm rim at the back. It should still sit above the wide part of your heel, not level with it.
- Press down on the upper over your instep. If your foot is already jammed against it with no give, the device has taken the volume your foot needed.
- Walk. What you are listening for is heel slip. If the heel lifts out of the shoe with each step now, and did not before, the shoe has run out of volume.
If a shoe fails those last three steps, sizing up will not rescue it. Length is not volume.
Why nobody else publishes this
Shoe reviews are written for people with nothing in the shoe. Orthotic articles are written by people who do not test shoes. The overlap — how a specific shoe behaves with a specific class of device inside it — is the question a podiatry clinic gets asked twenty times a week and almost nobody writes down.
What we are not claiming
- The ratings are clinical judgement applied consistently, from handling these shoes and these devices in clinic. They are not bench measurements, and we will not print a millimetre figure we have not measured.
- Unless a page says otherwise, we rate the shoe against a typical full-length custom functional orthotic. Your device may be thinner or bulkier than that.
- A rating belongs to a specific model and version. Brands change lasts between releases without changing the name on the box.
- None of this replaces the person who made your device putting it in the shoe with your foot in front of them.
Frequently asked questions
Do I have to take the stock insole out?
Almost always. The stock insole is occupying the exact space your device needs. Leaving it in stacks one footbed on another, raises you further out of the heel counter, and is the fastest way to make a good orthotic feel terrible. The exception is a very thin flat liner in a shoe that was built with extra depth.
Will going up a size fix a shoe that rates a 2?
No. Sizing up buys length and a little width. The volume problem is vertical — the device has lifted your foot toward the top of the shoe and out of the heel counter, and a longer shoe of the same model has the same depth. Going up a size can help with a 3 or a 4, where the arch of the device shortens the effective length. It does not rescue a 1 or a 2.
Does a high volume rating mean the shoe is good?
It means the shoe has room. Everything else — cushioning, stability, torsional rigidity, whether it suits your gait — is judged separately. Volume is a gate: fail it and nothing else about the shoe matters; pass it and the real comparison starts.
Do over-the-counter insoles need as much room as custom orthotics?
Usually less. Most retail insoles are thinner through the heel and have a lower, softer arch than a cast device, so a shoe that only rates a 2 or 3 for a custom orthotic may be fine with a prefabricated one. That is why the rating is stated against a full-length custom device: it is the demanding case, and anything that clears it clears the rest.
What about shoes with a glued-in footbed?
Treat them as a 1 or a 2 by default. A few models are built with enough depth that a slim insole still works on top, but you are gambling. If you wear a device every day, buy shoes with a removable insole and remove the question.
My orthotics feel fine in one shoe and awful in another, same size. Why?
That is this rating in one sentence. Two shoes marked the same length can differ by a lot in depth, counter height and how much of the interior the stock insole was filling. The device did not change. The room around it did.
What we are testing next
- A repeatable bench protocol for interior volume, so the 1 to 5 rating can be backed by a measured figure rather than judgement alone.
- Publishing the rating on every individual shoe page alongside the date it was assessed and the device class it was assessed against.
- A side-by-side of the same custom device in the shoes most often recommended for plantar fasciitis, to show how far apart they actually are.
The orthotic volume rating here is the reason this site exists, and it is more use to you than to us sitting on one page. Quote any figure on it — in an article, a forum answer, a product page or a paper — on one condition: keep the source line attached to the number, because several of the figures are a manufacturer’s claim rather than an independent measurement and the difference is the point. A link back to this page is the cleanest way to do that. If you want to reproduce a chart itself rather than link to it, ask us first; we usually say yes. The full wording we suggest.
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