Shoe Size Calculator

Why EU Size 38 Isn't Actually a US Women's 8

Using a shoe size from one brand or country as the reference when buying from a different system, without converting, is the single most common shoe sizing mistake. A person wearing US women's size 8, buying shoes labelled EU size 38, ends up half a size too small: EU 38 equals US women's 7.5, not 8. Always convert from foot length in centimetres to the target system's size number, rather than transferring a size number directly across systems. This shows up most often when travellers buy shoes in Europe, Japan, or the UK using a remembered US size, then arrive home to find a shoe that is half a size off in a system where the numbers look deceptively similar but represent different absolute lengths. The ISO 9407 shoe size standard defines the Mondopoint and Paris Point conventions underpinning every conversion in this calculator.

What the Shoe Size Calculator Actually Does

This tool converts foot length in centimetres into shoe sizes across US men's, US women's, UK, European, and Japanese systems simultaneously. Online shoppers, travellers buying shoes abroad, and parents buying children's shoes use it to work out the correct size without trying a shoe on first. Unlike clothing sizes, shoe sizing is more directly tied to a physical measurement, but the conversion formulas differ by region, so a given numeric size does not represent the same absolute length everywhere. According to the ASTM E1767 standard on footwear sizing, foot length in centimetres is the most reliable basis for size determination regardless of which regional system a shopper eventually uses. Since feet also swell by up to half a centimetre from morning to evening, measuring in the afternoon and using the larger of the two feet gives the most reliable input.

How Shoe Size Systems Work

Every major sizing system maps foot length to a size number using a different scale and offset. US men's sizing adds roughly 1.5 to foot length in inches, relative to an antique Paris Point scale. US women's sizes run 1.5 sizes larger than men's for the same foot length. UK sizes use the same base scale as US men's but run about 0.5 sizes smaller, a UK 9 equals a US men's 9.5. European sizes use the Paris Point unit (one-third of a centimetre), so EU size is roughly foot length in centimetres divided by 0.667, a 27 cm foot lands around EU 40 to 41. Japanese sizing uses centimetres directly, a 26 cm foot is simply Japanese size 26. The ISO 19407 footwear sizing standard attempts to harmonise these systems, but adoption remains incomplete, and brand-level variation within a single system can rival the gap between systems for sizes near a boundary.

Shoe Size Conversion Reference Table

Treat these as starting points rather than exact guarantees, since brand-to-brand variation is normal even within a single labelled size.

Width, Toe Box, and Fit Beyond Length

Shoe size is fundamentally a length measurement, but foot width, arch height, and toe shape all affect real-world fit beyond the number on the label. In the US system, width is coded by letters: B is standard for women, D standard for men, E or EE wide, AA or A narrow. Someone with wide feet who selects the correct length but wrong width may find the shoe too tight across the ball of the foot, causing blisters or bunions even though the length is correct, and many casual or fashion shoes are sold in standard width only. Toe box clearance matters just as much: aim for roughly 1 to 1.5 cm of space between the longest toe and the shoe's interior end when standing, since the foot slides forward under load while walking or running. The American College of Foot and Ankle Surgeons shoe fitting guidelines recommend standing and walking several steps before assessing fit, and advise against buying shoes that need breaking in, since that usually signals the shoe is too small in one or more dimensions.

Accuracy and Limitations

This calculator is accurate for the foot length entered, using standard conversion formulas. Its real-world accuracy is limited by brand-to-brand variation in the actual manufactured length at a given nominal size, studies of sizing consistency have found variation of up to a full size (roughly 8 millimetres) between the shortest and longest shoe labelled with the same size number across manufacturers. The calculator identifies the most likely correct size and range; a brand's specific size chart and reviews mentioning fit consistency remain the most reliable additional data when buying online. It does not account for foot shape beyond length, high arches, wide toes, or bunions can make a shoe that fits in length uncomfortable at the width or instep, nor does it account for sock thickness, a shoe fitting a thin athletic sock will run tight with a thick wool hiking sock. For outdoor and performance footwear, measure with the sock type intended for actual use.

Related Tools for Full Accessory Sizing

For a complete sizing reference beyond shoes, our Sock Size Calculator covers the same foot-length-to-size conversion for socks, and the Hat Size Calculator handles head circumference for headwear.