One foot bigger than the other: how to buy shoes that fit both

Having one foot bigger than the other is the normal case, not the exception. Most people have a measurable difference between their feet, and most have never checked which one is larger.

This guide covers how to measure the difference, which foot to buy for, and how to make a single pair of shoes fit two slightly different feet.

Quick Summary

Buy for the larger foot, then take up the extra space in the smaller one. That order matters. A shoe that is too small cannot be fixed, while a shoe that is slightly too big has several good solutions.

• Differences are normal. Up to around half a size is common.
• Always fit the larger foot. Never average the two.
• Adjust the smaller side, with lacing, an insole or a tongue pad.
• Quarter sizing helps because it reduces how much you have to compensate.
• A new or large difference is worth getting looked at rather than fitting around.

How to handle each size gap:

How common is it?

Common enough that fitting both feet identically is the unusual approach rather than the standard one.

Most people have some difference between their feet, and a difference of up to about half a size is routine. Shoe fitters work on the assumption that the two feet will not match, which is why a good fitting always involves measuring both.

What this means practically is that the single number you think of as your shoe size is really the size of your larger foot, or should be. If you have been buying by the smaller one, the larger foot has been cramped for years.

Why are feet different sizes?

Several reasons, most of them unremarkable.

• Normal asymmetry. Bodies are not symmetrical. Hands differ too, we just do not buy fitted gloves.
• Dominance. The foot you push off with, pivot on or kick with can develop differently.
• Old injuries. A previous fracture, sprain or surgery can change shape or swelling patterns.
• Arch difference. One foot with a lower arch will measure longer under load.
• Swelling. One foot may swell more, which is a size change rather than a structural one.

The first three are structural and permanent, which is fine and simply needs fitting around. The last two are worth distinguishing, because an arch that has dropped or a foot that swells persistently on one side is a different conversation from lifelong asymmetry.

How do you measure the difference?

Properly, at home, in about five minutes. The key is doing both feet under weight.

1. Measure in the evening. Feet are at their largest after a day of use.
2. Wear the socks you will wear with the shoes.
3. Stand on a sheet of paper with your weight on that foot. Sitting gives a shorter measurement.
4. Mark the heel and the longest toe. The longest toe is not always the big toe.
5. Measure the distance, then repeat for the other foot on a fresh sheet.
6. Measure width too, across the widest part of the ball of the foot.

Write both numbers down rather than trusting your memory of which foot felt bigger. People are frequently wrong about which of their own feet is larger, because the one that feels tight in a shoe is sometimes the narrower one rather than the longer one.

The complete fitting method is in how should sneakers fit, and for converting between systems there are guides for UK to US and EU to US sizes.

Which foot should you buy for?

The larger one, without exception, and the reasoning is asymmetric.

A shoe that is too short cannot be made longer. The foot has nowhere to go, the toes press the end, the shoe flexes in the wrong place, and the result over time is discomfort at best. There is no accessory that fixes a shoe that is too small.

A shoe that is slightly too long, by contrast, has several good fixes, all of which work by taking up volume. That asymmetry is the whole reason the rule exists.

The temptation is to split the difference and buy a size between the two, which leaves the larger foot slightly cramped and the smaller one slightly loose. That gives you two badly fitting shoes instead of one well fitting and one adjustable.

How does lacing fix the smaller side?

By changing where the shoe grips, which is usually enough for differences up to about half a size.

The common mistake is pulling the whole lace tighter, which compresses the forefoot and causes pressure across the top of the foot. What works better is targeted lacing.

• Use the top eyelet. Most people skip it, and it is what anchors the heel.
• Heel lock lacing. Threading the lace back through itself at the top creates a loop that holds the heel without tightening the forefoot. It takes thirty seconds and solves a lot of cases.
• Skip an eyelet over a sensitive area to relieve one specific pressure point.
• Tighten the upper half only, leaving the forefoot relaxed, when the problem is heel slip rather than overall looseness.

Heel lock lacing is the single most useful technique here and the least known. It is worth learning before buying any accessory.

When should you add an insole?

When lacing alone leaves the smaller foot moving, which is usually from about half a size of difference upward.

A thin full length insole in the shoe on the smaller foot takes up volume throughout, which shortens the effective internal length slightly and raises the foot so the upper holds it better. This is the cleanest fix because it does not create a localised pressure point.

Two things to check. The shoe needs enough depth, which usually means removing the existing footbed rather than stacking on top of it. And the insole should be full length rather than a heel pad, because a heel only insert tips the foot forward.

If the shoe has a glued in footbed there is no room to do this, which is a good argument for buying shoes with a removable one. What is the insole of a shoe explains the layer.

What about tongue pads and heel grips?

Both are useful for specific symptoms rather than general looseness.

A tongue pad sits under the tongue and pushes the top of the foot down and back into the heel of the shoe. It is the right fix when the foot slides forward in the shoe, and it works surprisingly well for a shoe that is slightly too long.

A heel grip lines the back of the heel counter, adding a few millimetres and increasing friction. It is the right fix for heel slip specifically, where the heel lifts out of the shoe as you walk.

Both are inexpensive and reversible, which makes them worth trying before concluding a shoe does not fit. Used together with a thin insole they can comfortably handle a full size of difference.

Why does quarter sizing matter here?

Because it reduces the size of the problem rather than solving it after the fact.

With half size increments, a foot that sits between two sizes forces a choice: slightly too small, or slightly too big and needing adjustment. With quarter sizes, the larger foot can usually be fitted closer to its actual length, which means there is less excess to take up on the smaller side.

The effect compounds with an asymmetric pair. If your larger foot is fitted precisely rather than rounded up, the gap you are compensating for on the smaller foot is the real difference between your feet rather than that difference plus a rounding error.

What if the difference is width, not length?

Then the approach inverts slightly: fit the wider foot, and take up volume on the narrower one.

Width differences are less often noticed because people think of sizing as a length problem. A foot that is the same length but noticeably wider will feel tight across the ball in a shoe that fits the other foot fine, and no amount of length adjustment helps.

The fixes are the same tools in a different order: a shoe with a roomier toe box fitted to the wider foot, then a thin insole or a tongue pad to stop the narrower foot sliding. A shoe with a soft, giving upper handles a width difference far better than a structured one.

Wide toe box shoes and what is B width in shoes cover width specifically.

Can you buy two different sizes?

Sometimes, and it is worth asking about if your difference is large.

Some retailers and manufacturers will accommodate split size pairs, usually on request rather than as a standard option, and occasionally for a fee. It is most commonly available where a difference is significant enough that adjustment will not bridge it.

The other route some people take is buying two pairs and keeping the spare shoes, which works but is expensive and leaves you with odd shoes. For most differences, adjusting one shoe of a normal pair is the more practical answer.

Where the difference is large, a professional fitting is worth the time. A fitter sees asymmetric feet constantly and will know what the available options actually are.

When is a difference worth checking?

• A difference that is new. Feet that used to match and now do not.
• A difference of more than about a size, particularly if it appeared in adulthood.
• One foot that swells and the other that does not.
• An arch that has flattened on one side.
• Pain, numbness or weakness on the larger side.
• Visible change in shape rather than just size.

Lifelong asymmetry is a fitting problem. A change in asymmetry is a different question, and swelling on one side in particular is worth a professional opinion rather than a shoe adjustment.

On swelling specifically, shoes for swollen feet covers what changes, and an arch that has dropped recently is covered in best shoes for flat feet.

Where does Atoms fit?

This is one of the few fit problems where the sizing system itself is the relevant feature.

From Atoms' published specifications, the Model 000 is sized in quarter increments from US 3.5 to 15 in one unisex run, with a knit upper, stretch laces, a removable insole that fits custom orthotics, a firm and secure heel cup with a wide heel counter, and a wide forefoot.

Four of those help with asymmetric feet.

What no sizing system solves is a difference of two sizes or more, which needs either split sizing or a fitting rather than a feature.

How to start

Measure both feet this evening, standing, in the socks you actually wear. Write down both lengths and both widths.

Buy for the larger foot. Then work through the adjustments in order of cost on the smaller side: lacing first, then a thin insole, then a tongue pad or heel grip. Most differences are fully handled by the first two.

Frequently asked questions

Is it normal to have one foot bigger than the other?

Yes, it is the normal case rather than the exception. Most people have a measurable difference, and up to around half a size is routine. Good shoe fitters always measure both feet for this reason.

Which foot should you buy shoes for?

The larger one, always. A shoe that is too short cannot be made longer and no accessory fixes it. A shoe that is slightly too long has several good fixes that work by taking up volume, which is why the rule is asymmetric.

How do you measure the difference between your feet?

In the evening, in the socks you will wear, standing with your weight on the foot being measured. Mark the heel and the longest toe on paper, measure, then repeat on a fresh sheet for the other foot. Measure width too.

Why is one foot bigger than the other?

Usually normal body asymmetry, foot dominance, an old injury, or a difference in arch height that makes one foot measure longer under load. Swelling on one side is a different thing and worth distinguishing.

How do you make a shoe fit a smaller foot?

Work up in order of cost. Lacing first, especially using the top eyelet and a heel lock pattern. Then a thin full length insole. Then a tongue pad or heel grip. The first two handle most differences.

Where should a heel grip or tongue pad go?

A heel grip lines the back of the heel counter and fixes heel slip specifically. A tongue pad sits under the tongue and pushes the foot back into the heel, which is the right fix when the foot slides forward in a shoe that is slightly too long.

Does quarter sizing help with mismatched feet?

Yes, because it reduces the size of the problem. The larger foot can be fitted closer to its actual length, so the gap you compensate for on the smaller side is the real difference rather than that difference plus a rounding error.

Can you buy two different shoe sizes?

Sometimes. Some retailers and manufacturers accommodate split size pairs on request, usually where the difference is large enough that adjustment will not bridge it. For most differences, adjusting one shoe of a normal pair is more practical.

What if the difference is width rather than length?

Fit the wider foot and take up volume on the narrower one with a thin insole or tongue pad. A shoe with a soft giving upper handles a width difference far better than a structured one.

When is a size difference worth checking?

If it is new, more than about a size, appeared in adulthood, involves swelling on one side only, or comes with pain, numbness or weakness. Lifelong asymmetry is a fitting problem. A change in asymmetry is a different question.