Shoe Size Converter

Why shoe size conversions matter for international shopping

Shopping for shoes online has never been easier — you can buy directly from brands and retailers across the US, UK, Europe, Japan and beyond. But the world's shoe sizing systems are inconsistently related, and buying the wrong size is one of the most common and frustrating online shopping mistakes. A size 10 in the US is not a size 10 in the UK or Europe, and converting correctly between systems is the difference between a perfect fit and a return shipment.

This free shoe size converter covers all major international systems: US men's and women's, UK, European (EU), Japanese/Korean (in cm), and Mexican sizing — and the universal anchor that makes all conversions reliable: your foot length in centimetres. The cm measurement is the one true reference point that eliminates all regional ambiguity. If you know your foot length, you can find your size in any system instantly with this chart and converter.

A brief history of shoe sizing systems

Modern shoe sizing systems evolved independently in different countries, which is why they are so inconsistent today. The UK system, dating to King Edward II in 1324, defined the barleycorn (1/3 inch, approximately 8.5 mm) as the increment between sizes, starting from a size 0 set equal to a child's foot of 4 inches. The US system adopted a similar barleycorn increment but started at a different size 0 baseline, creating the persistent half-size offset from UK sizes. The European Mondopoint system (ISO 9407), adopted in the 1970s, replaced historical country-specific systems with a purely metric, foot-length-based standard, making EU sizing the most rational of the common systems. Japan and Korea similarly adopted direct centimetre measurements.

Men's vs. women's sizing: what you need to know

The most confusing aspect of US shoe sizing is the separate male/female scales. Women's shoes run approximately 1.5 sizes larger than men's for the same foot length — so a US women's size 9 and a US men's size 7.5 fit the same foot. This gap exists because men's and women's lasts (the foot-shaped forms) were developed historically on different average foot shapes, not just different sizes.

In contrast, EU sizing is genuinely unisex — EU 42 is always approximately 26.5–27 cm of foot length, regardless of whether the shoe is marketed as men's or women's. This is why many runners and online shoppers prefer using EU sizes when comparing products across brands and genders. Our international shoe size chart shows both US men's and women's equivalents for every EU size so you can shop confidently across any regional listing.

How to measure your foot and find your true size

The most reliable way to find your correct shoe size is to measure your foot length directly rather than relying on a remembered size from years ago (feet change with age and weight). Stand on a piece of paper with your heel touching a wall, trace your foot outline, and measure the straight-line distance from heel to longest toe. Measure in the afternoon, as feet naturally swell by up to half a size over the course of the day. Measure both feet and use the larger measurement.

Enter your foot length in the converter above and instantly see the equivalent size in every major system. When buying online, always cross-reference your converted size against the specific brand's own size chart — brands like Nike, Adidas, New Balance and Converse each have their own fitting quirks that can shift your best size by half a size in either direction. Pair this shoe size chart with brand reviews that mention sizing feedback, and you will almost always get the right fit on the first order.

Buying shoes online: brand-by-brand sizing differences

Generic shoe size charts give you a starting point, but brand-specific lasts and construction choices mean the same EU or US size fits differently across labels. Nike shoes generally run half a size small, so if you measure EU 42 you should typically order EU 42.5. Adidas runs close to true size but some models (particularly Ultraboost) are slightly narrow in the toe box. New Balance tends to run true-to-size or a touch large and offers genuine wide-width options (2E/4E) that most other brands don't. Converse typically runs a full size large — a US men's 10 should order a 9 in Converse.

When shopping internationally, the return window matters as much as the size chart. ASOS offers free returns to many countries; Zalando gives 100 days; direct Nike and Adidas stores often allow in-store returns of online purchases. Use this shoe size converter to find your starting size, factor in brand-specific fit notes from reviews, and buy from a retailer with a generous return policy so you can exchange if the first pair is slightly off.

Children's and toddler shoe sizing: what parents need to know

Children's shoe sizing follows its own progression that is entirely separate from adult scales. In the US, infant sizes begin at 0 (newborn, roughly a 3.5-inch / 8.9 cm foot) and run through size 4 or so. Toddler sizes pick up from size 1 (approximately 3.75 inches / 9.5 cm) and continue to around size 10, at which point the little kid scale begins (sizes 10.5–3) before transitioning into big kid sizes (3.5–7), which bridge into the adult scale. EU sizing sidesteps all of this complexity because it uses a single unisex number line for both children and adults — EU 16 fits a newborn, and the numbers simply increase as the foot grows, connecting seamlessly into adult EU sizes in the 30s and 40s.

Children's feet grow at a pace that surprises most first-time parents. On average, a child's foot grows two or more sizes per year during the first five years of life, slowing to roughly one size per year through the early school years. In practical terms, toddlers often need new shoes every two to four months. The standard fitting rule is the thumb's-width check: press your thumb between the end of the shoe and the child's longest toe — there should be about one thumb's width (roughly 1 cm) of space to accommodate growth and natural foot movement while walking. Less than that and the shoe is already too small; significantly more and the shoe will cause tripping and blisters.

The most accurate way to measure a child's foot is with a Brannock device, the metal measuring tool found in most shoe stores, which simultaneously captures heel-to-toe length and arch length. At home, the paper-trace method works well: stand the child on paper, trace around the foot, and measure heel to longest toe. Always measure both feet (children's feet are often slightly different lengths) and fit to the larger one. Measure while the child is standing and bearing full weight, since feet spread slightly under load — the difference matters for a correct fit.

The last: how shoe construction shapes fit beyond size numbers

A last is the three-dimensional foot-shaped form around which a shoe is constructed. Every measurement of a shoe — its length, width, toe-box height, arch profile and heel cup — derives from the last used to build it. Two shoes bearing identical size labels can fit completely differently if they were built on different lasts, which is why brand-to-brand size variation is not merely about measurement inconsistency but about fundamentally different design intentions. Understanding lasts explains why your EU 42 Adidas Ultraboost may be comfortable while an EU 42 Adidas Copa soccer cleat feels cramped: the two products were built on lasts designed for entirely different performance requirements.

Athletic lasts are engineered to be more generous in the forefoot and toe box, allowing toes to splay naturally during movement and providing volume for feet that swell during prolonged activity. Fashion or dress lasts are typically longer, narrower and more tapered toward the toe — they are shaped around an aesthetic ideal rather than biomechanical function, which is why dress shoes often require a break-in period and why many people size up half a size when buying leather dress shoes. The practical takeaway: never assume that a size that fits in one shoe category will fit the same in another category, even from the same brand.

Last material also plays a role in fit precision. Mass-produced footwear uses plastic or aluminium lasts that are durable and consistent across production runs. Bespoke and artisan shoemakers carve wooden lasts that can be individually modified to accommodate a specific client's foot anatomy — bunions, high arches, asymmetric foot lengths. The width grading system (the US letter system of B, D, 2E, 4E and so on) attempts to codify last volume for the consumer, but in practice few brands label width consistently, and genuine wide-width lasts (2E and 4E) are only reliably available from brands that specifically market wide-fit lines such as New Balance, Brooks and ASICS.

Mondopoint: the rational ISO standard hiding in plain sight

Mondopoint (ISO 9407) is the only international shoe sizing standard based entirely on metric measurement. A Mondopoint size is expressed as foot length in millimetres divided by 5, with an optional second number representing foot circumference at the ball of the foot in millimetres. So a size 260/98 means a foot that is 260 mm long with a 98 mm ball circumference — completely unambiguous, no regional interpretation required. Compare this to US men's size 8, which depending on the brand and manufacturing era could correspond to foot lengths anywhere from 255 mm to 267 mm.

Mondopoint is the mandated standard for NATO military footwear and is widely used in competitive athletics, ski boot manufacturing and some professional work-boot categories, where precise fit is critical and inconsistency has functional consequences. Many high-performance running shoe brands publish Mondopoint interior dimensions for their race shoes alongside their consumer size labels, allowing serious athletes to match a shoe's internal geometry precisely to their measured foot. If you have ever had trouble with sizing in specialty athletic footwear, looking up the Mondopoint spec is a reliable way to cut through brand-specific labelling variation.

Despite its obvious advantages, Mondopoint has made virtually no inroads in mainstream retail. Consumer habit is deeply entrenched around regional size numbers — people identify as a 'size 10' or an 'EU 44' in a way they would never say 'I am a Mondopoint 270.' Additionally, retail inventory systems built over decades are not designed to accommodate the two-dimensional (length × width) nature of the Mondopoint spec, and brands have no marketing incentive to highlight a standard that commoditises sizing across competitors. The result is that the most rational system in existence remains largely invisible to everyday shoppers, while the centimetre foot-length measurement — effectively the consumer-accessible proxy for Mondopoint — remains the most practical universal sizing anchor.

Athletic shoe fit by sport: why one size does not fit all activities

Fit requirements vary substantially across athletic shoe categories, and sizing up or down from your everyday shoe size is often correct — not a mistake. Running shoes should be fitted approximately half a size to a full size larger than your casual shoes. During a long run, feet can swell by a full size in volume; if your toes are pressed against the shoe's end, the repeated impact on a downhill or late in a race causes bruising under the nail — the classic black toenail of long-distance runners. The thumb's-width rule (one thumb's width between your longest toe and the shoe end, measured while standing) is the standard fitting check for running footwear.

Cycling shoes are typically fitted true to size or a half size up, not because of swelling but because cycling shoes are deliberately narrow and stiff to maximise power transfer to the pedal. Many cyclists with medium-width feet find they need to size up half a step to accommodate the narrower last. Hiking boots warrant sizing up a full size to allow for thick merino wool or technical hiking socks, and to accommodate the foot swelling that occurs over long days on the trail — a boot that fits perfectly in the morning will feel painfully tight by mile ten. Football and soccer cleats, by contrast, are commonly worn half a size to a full size smaller than running shoes, creating a snug fit that improves ball feel and reduces the unwanted foot movement inside the boot that blunts touch and control.

Material matters too when it comes to whether you can correct a slight misfit after purchase. Full-grain leather shoes and boots will stretch with wear, conforming over time to the exact shape of the foot — a leather dress shoe or hiking boot that is slightly snug but not painful will often fit well after a few uses. Synthetic uppers (mesh, knit, engineered textiles, most modern running and lifestyle shoes) have minimal stretch and will not adapt meaningfully to your foot. With synthetic shoes, the fit you feel in the store or on first wear is the fit you will always have — there is no break-in, and buying a slightly small pair hoping it will expand is a reliable route to discomfort.