Shoe Size Conversion

Shoe size is a complicated topic, mostly because there is no global standard. Differences in how size is measured and defined between countries, differences between men's and women's feet, the way brands label and manufacture their own shoes, and the plain fact that most people have two slightly different feet all contribute to the difficulty of pinning down a proper size.

Much of the reason for the missing standard is that shoemaking existed long before mass production. Shoes were made individually and fitted to the person in front of the cobbler, wherever that happened to be. That produced many different methods of measurement and fabrication, and no particular motivation for countries or even neighbouring regions to agree on one. As with units of measurement generally, once a tradition is established and ingrained it is difficult to change, even when a better system exists.

The calculator above estimates shoe size from foot length alone. Many other things affect how a shoe actually fits, and those are discussed further down, but foot length gives a consistent reference from which to start. The tables and formulas here are one interpretation of size based on foot length, and they may differ slightly from those published by other sites, manufacturers and brands.

Shoe size calculation formulas

US and Canada

where L is foot length in inches. In this system sizes increase in half-point steps.

UK and India

where L is foot length in inches, again in half-point steps. Notice that the UK adult formula subtracts 23 where the US men's formula subtracts 22, which is the whole reason a UK size runs roughly one number below the equivalent US men's size.

EU

where C is foot length in centimetres. EU sizes move in whole-point steps, which is why two adjacent US half sizes sometimes convert to the same EU number.

Japan and Mexico

where C is foot length in centimetres, in half-point steps. This is the most transparent system of the lot: the number on the shoe is simply the length of the foot it is meant to fit.

China

where C is foot length in centimetres, in whole-point steps.

Shoe size chart

The tables below are generated from the same formulas the calculator uses, so they agree with it exactly.

Women's shoes

Men's shoes

Infant and toddler shoes (age 0 to 4)

Kid's shoes (age 5 to 12)

Why the numbers are so different

English-speaking sizes descend from the barleycorn, an old unit equal to one third of an inch. Edward II is said to have standardised the inch as three barleycorns in 1324, and shoemakers took the barleycorn as their step between sizes. That is why a full size still changes the length by a third of an inch and a half size by a sixth, roughly 4.2 mm, and why the numbers look arbitrary: they count barleycorns from a zero point that nobody agreed on.

The US and UK scales use different zero points, which is the entire source of the roughly one-size offset between them. Women's and men's US sizes differ by about 1.5 for the same foot, again purely a labelling convention rather than anything physical.

Continental Europe took a different route with the Paris point, a step of two thirds of a centimetre, and measures the last rather than the foot, which is why EU numbers run so much higher. Japan and China simply use the foot length in centimetres, which is the most sensible approach and the least common.

Foot measurement systems

Shoe size estimation is based on measuring the foot. A given size is a function of the manufacturer, the shoe last (the physical form used to make and repair shoes), a country's standards and more. Several measurement systems exist, including the Brannock device, the RITZ stick and Mondopoint.

Brannock device

The Brannock device, the metal plate found in every shoe shop, takes three measurements that matter for fit:

• Foot length, from the heel to the longest toe.
• Foot width, across the ball of the foot.
• Arch length, from the heel to the inside of the ball of the foot.

Charles Brannock developed it in 1927 and patented it the following year, and the design has barely changed since. It is the preferred device for many professionals, though it still does not capture everything that affects size, such as the circumference of the ball of the foot or heel width. It corresponds to the Brannock sizing system, which gives primarily US sizes and may differ slightly from the ones this calculator produces. In that system:

US men's size = (foot length in inches × 3) − 22

US women's size = (foot length in inches × 3) − 21

The arch length measurement is the one people ignore and shouldn't. The shoe needs to flex where your foot flexes, so a foot with a long arch may need a larger size than its length alone suggests, and the Brannock instruction is to take the larger of the two readings.

RITZ stick

The RITZ stick was the standard measuring device before the Brannock device arrived. It is a wooden slide rule with men's and women's sizes along it and a conversion chart on the reverse for moving between width and length. Both it and the Brannock device are only partly effective at assessing size, because so many other factors affect fit. They are useful for a quick measurement, and the size that comes out is one input among several.

Mondopoint

Mondopoint is used across the sports industry for ski boots, skates and ballet shoes, and as the primary sizing system in parts of the world including Russia, China, Japan and South Korea. Standardised as ISO 9407, it is based on the average foot length and width a given shoe suits, measured in millimetres:

• Foot length, the horizontal distance between the perpendicular at the back of the heel and the perpendicular at the longest toe.
• Foot width, the horizontal distance between the first and fifth metatarsophalangeal joints.
• Perimeter, the circumference around those same two joints, taken with a flexible tape.

Mondopoint varies slightly by country but the concept is constant. Because it accounts for width and circumference rather than length alone, it generally fits better than systems built on a single measurement. A Mondopoint size such as 270/100 says the shoe suits a 270 mm foot 100 mm wide, which is far more information than the number 9.

How to find the right shoe

Several things determine how well a shoe fits:

• Foot length. An important estimator, but two people with identical foot length can find the same shoe fits very differently, and the same person will take different sizes across brands and even across models within one brand. It is a starting point rather than an answer.
• Foot width. The width at the widest point matters, and so does the width along the rest of the foot. Width sizing exists, running from AAA through to EEE in the US system, but there is no real standard for labelling it and designations vary by manufacturer and country.
• Foot shape. Circumference, instep height and where the arch sits all affect which shoe suits, independently of length and width.
• Sex. Men and women have differently shaped feet. Men's are generally longer and broader, but the differences extend to shape: women's feet are not scaled-down men's feet, differing around the arch, the lateral side, the first toe and the ball. Converting between the two scales gives a number, not necessarily a fit.
• Age. Feet change over a lifetime. Ligaments and tendons loosen with age, so feet lengthen and widen, and someone who wore a 9 for thirty years may genuinely need a 10 later on.
• Manufacturer. Different brands use different lasts and processes, so length, width and overall fit vary between shoes labelled the same size. This is the single biggest reason a converted number is a starting point rather than a guarantee.

Ideally, try the shoe on and spend some time in it. Size is a good starting point, and fit is difficult to judge from a number alone.

How to measure your foot

• Measure later in the day. Feet swell as the day goes on, by up to about 8% for some people, so a morning measurement gives a shoe that pinches by evening.
• Use a Brannock device or similar where you can, since it gives a more reliable reading than a household ruler.
• Fit to your larger foot. Most people have two slightly different feet, and it is better for a shoe to be marginally loose than marginally tight. How much room to leave depends on use: shoes worn for long periods or hard wear want space for swelling, while sports such as climbing trade comfort for precision deliberately.
• Measure standing, with weight on the foot, since the foot spreads under load. Measuring seated understates the length.
• Wear the socks you intend to use with the shoe, which can easily account for a half size on its own.

Two last practical points. Sizes are not consistent even within a brand across seasons, and vanity sizing, where a maker labels a shoe smaller than it measures, is common enough in fashion footwear to be worth knowing about. And if you sit between sizes, the shape of the shoe usually matters more than the number: a roomy 8 will beat a narrow 8.5 for a wide foot every time.