What Shoe Size Should I Buy When Wearing Orthotics?

An orthotic device sits inside your shoe and takes up space that was not 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 may press against the front, your foot may feel cramped across the top, and your heel may slip upward because the shoe is now too shallow to hold it in place.

The solution 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 device to the shop and test it in the actual shoe before buying. Every shoe fits differently, and the only reliable way to confirm the right size is to try it.

Going up a size can introduce heel slip, where your heel lifts out of the shoe with each step. This does not mean the shoe is wrong. It means you need to secure the fit around the instep. Try the following:

• Look for a padded heel collar: a cushioned rim around the top of the heel cup reduces movement and improves comfort.
• 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: adjustable fastening lets you lock the midfoot down, which stops the heel from lifting.

It is completely normal for one foot to be larger than the other. When orthotics are involved, the difference can feel more pronounced because the device amplifies any size mismatch. Here is what to do:

• Size for the larger foot: always fit the shoe to whichever foot needs the orthotic most, or whichever foot is bigger.
• Ask about split-size purchasing: some specialist retailers will sell you two different sizes as a pair. This is 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 can reduce excess movement.

When getting your feet measured for orthotic-compatible shoes, follow this process for the most accurate result:

• 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. Do not sit or perch on the edge of a chair.
• Measure both feet. The difference between them may be greater than you expect.
• Measure later in the day if possible, as feet swell slightly throughout the day and you want the most generous 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 is a 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 generous and realistic reading. This is especially important when you are accommodating an orthotic device.

My NHS orthotist did not advise on shoe size. What should I do?

This is 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, or visit a specialist retailer who is experienced in fitting shoes for orthotics.

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

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

Can I rely on an online size chart?

Online size charts are a starting point only. They do not account for the extra volume of an orthotic. If you are buying online, order your usual size and one size up, then return whichever does not 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.