What Shoe Size Should I Buy When Wearing Orthotics?

An orthotic sits inside your shoe and takes up space that wasn't there before. Even a thin over-the-counter insole adds height and volume. A thicker custom device adds considerably more.

That extra volume makes the shoe tighter. Your toes press against the front, the top of your foot feels cramped, or your heel slips because the shoe is now too shallow to hold it properly.

The fix is straightforward: you usually need a slightly bigger shoe. The question is how much bigger.

The amount of extra size you need depends primarily on the thickness of your orthotic device. Use the table below as a starting point:

Device Type	Typical Size Adjustment
Thin over-the-counter insole	Half a size up
Standard custom orthotic	One full size up
Thick or heavily contoured custom orthotic	One to one-and-a-half sizes up
Ankle-foot orthosis (AFO)	At least one full size up

Important: these are guidelines, not rules. Always bring your orthotic to the shop and try it in the actual shoe. Every shoe fits differently, and there's no substitute for testing it yourself.

Going up a size can introduce heel slip, where your heel lifts out of the shoe with each step. That doesn't mean the shoe is wrong. It means you need to secure the fit around the instep. Here's what I recommend:

• Look for a padded heel collar: a cushioned rim around the top of the heel cup reduces movement and makes the fit more comfortable.
• Choose shoes with a firm heel counter: a rigid heel cup holds the foot in place even when the shoe is slightly larger than usual.
• Use laces or Velcro to snug the instep: locking the midfoot down stops the heel from lifting.

It's completely normal for one foot to be larger than the other. I'd say the majority of people I fit have at least a small difference. When orthotics are involved, that mismatch becomes more obvious because the device takes up space. Here's what to do:

• Size for the larger foot: always fit the shoe to whichever foot is bigger or whichever needs the orthotic most.
• Ask about split-size purchasing: some specialist retailers will sell you two different sizes as a pair. It's more common with orthotic-focused brands.
• Use a heel grip on the smaller foot: a simple adhesive heel pad inside the shoe on the smaller side reduces excess movement nicely.

When getting measured for orthotic-compatible shoes, follow this process:

• Place your orthotic inside your sock before stepping onto the measuring device, or hold it against the sole of your foot.
• Stand with your full weight on both feet. Don't sit or perch on the edge of a chair.
• Measure both feet. The difference between them may be bigger than you'd expect.
• Measure later in the day if you can. Feet swell throughout the day, and you want the most realistic measurement.

Width matters just as much as length when fitting shoes for orthotics. UK shoe widths use a letter system, but not all retailers display them clearly. Here's a quick reference:

Width Code	Description
D (or unmarked)	Standard width
E	Wide
EE / 2E	Extra wide
EEE / 3E	Very wide

If your orthotic is thick or heavily contoured, you may need a wider fitting than you normally wear. Going wider can sometimes reduce the need to go up a full size in length.

Should I measure my feet in the morning or the evening?

Evening is better. Feet swell during the day, so measuring later gives you the most realistic reading. This matters even more when you're accommodating an orthotic.

My NHS orthotist didn't advise on shoe size. What should I do?

This is really common. Not all clinics have time to cover shoe fitting in detail. Call your orthotics department and ask whether they can recommend a size adjustment for your specific device. Alternatively, visit a specialist retailer who's experienced in fitting shoes for orthotics.

My toes are hitting the front of the shoe. Is it the wrong size?

Possibly, but the orthotic may also be pushing your foot forward inside the shoe. Try a shoe with a roomier toe box, or go up half a size. If the problem continues, speak to your orthotist.

Can I rely on an online size chart?

Size charts are a starting point only. They don't account for the extra volume of an orthotic. If you're buying online, order your usual size and one size up, then return whichever doesn't work. Always check the retailer's returns policy first.

Buying for a child? Children's sizing works differently and changes rapidly. Read our guide on what size shoes to buy for a child wearing orthotics.

Browse our full Orthotic Shoe Buyer Guide for more detailed advice on every aspect of buying shoes for orthotics.