Why shoe sizes are a mess
Buying shoes from a brand based in another country sounds easy until you hit the size chart. You're a US men's 9. The Italian brand lists EU 42, 42.5, and 43. The Japanese brand lists 27 cm and 27.5 cm. The UK brand lists 8 and 8.5. Same foot, four different numbers — and none of them line up the way you'd expect.
That's because shoe sizing was never really designed. It accumulated. The US system traces back to the Brannock device, a foot-measuring tool patented in 1925. The UK uses a similar measure but offsets the numbering. The EU uses the Paris point — a unit equal to two-thirds of a centimeter — that French shoemakers picked in the early 1800s. Japan skipped all of that and uses Mondopoint, which is just foot length in centimeters.
The Shoe Size Conversion tool translates between all four. Pick your category (men's, women's, or kids'), pick the system you know, type your size, and you get the equivalents in the other three plus the Mondopoint foot length. No formula, no math — shoe sizing isn't actually mathematical. The tool reads off a reference table that every shoe-industry handbook uses.
The four systems, in plain language
US (Brannock). Whole and half sizes, with men's and women's on different scales. The women's scale is offset by about 1.5 sizes from men's, so a women's 9 is roughly the same length as a men's 7.5. Width is a separate letter dimension (B, D, EE, etc.) that the calculator doesn't cover.
UK. Numerically close to US but offset. A US men's 9 is roughly a UK 8.5. Used in the UK, Ireland, and parts of the Commonwealth. UK women's sizing was historically on the same scale as men's, though some retailers now use the US-style offset to match American conventions.
EU. One unified scale for adults — a 38 is a 38 regardless of who's wearing it. The numbers come from the Paris point, where each size represents two-thirds of a centimeter of last length. Most EU sizes are whole numbers (40, 41, 42), but half sizes show up on Italian and French stock.
Japan (Mondopoint). Foot length in centimeters. A JP 27 shoe is built on a 27 cm last. This is the cleanest system — no offsets, no gender split, no historical baggage. The downside is it ignores width entirely.
Worked example: a US men's 9
Say you wear a US men's 9 and you're shopping online from a brand that only lists EU and JP sizes. Here's what the tool tells you:
US men's 9
UK: 8.5
EU: 42–43 (typically 42.5)
Japan: 27 cm
Foot length: ~270 mm
Notice that the EU number isn't a single value. That's because EU sizes step in two-thirds of a centimeter, and the gap between US 9 and US 9.5 doesn't land exactly on a Paris point. Different brands round this gap differently — Italian makers tend to stock the half-point sizes (42.5), German and Spanish brands often don't. If the retailer only carries whole EU sizes, you'd typically pick 42 if you have a snug-fitting foot or 43 if you prefer a little room.
Adult men's conversion table
| US Men's | UK | EU | JP / cm |
|---|---|---|---|
| 6 | 5.5 | 39 | 24 |
| 6.5 | 6 | 39.5 | 24.5 |
| 7 | 6.5 | 40 | 25 |
| 7.5 | 7 | 40.5 | 25.5 |
| 8 | 7.5 | 41 | 26 |
| 8.5 | 8 | 42 | 26.5 |
| 9 | 8.5 | 42.5 | 27 |
| 9.5 | 9 | 43 | 27.5 |
| 10 | 9.5 | 44 | 28 |
| 10.5 | 10 | 44.5 | 28.5 |
| 11 | 10.5 | 45 | 29 |
| 11.5 | 11 | 45.5 | 29.5 |
| 12 | 11.5 | 46 | 30 |
| 13 | 12.5 | 47 | 31 |
| 14 | 13.5 | 48 | 32 |
Adult women's conversion table
| US Women's | UK | EU | JP / cm |
|---|---|---|---|
| 5 | 2.5 | 35 | 22 |
| 5.5 | 3 | 35.5 | 22.5 |
| 6 | 3.5 | 36 | 23 |
| 6.5 | 4 | 37 | 23.5 |
| 7 | 4.5 | 37.5 | 24 |
| 7.5 | 5 | 38 | 24.5 |
| 8 | 5.5 | 38.5 | 25 |
| 8.5 | 6 | 39 | 25.5 |
| 9 | 6.5 | 40 | 26 |
| 9.5 | 7 | 40.5 | 26.5 |
| 10 | 7.5 | 41 | 27 |
| 10.5 | 8 | 42 | 27.5 |
| 11 | 8.5 | 42.5 | 28 |
Notice that women's US 9 lines up with men's US 7.5 — same foot length, different number on the box. That's the 1.5-size offset baked into US (and to a lesser extent UK) women's sizing. The EU column is gender-neutral, so a women's US 9 and a men's US 7.5 both map to EU 40–40.5. Same shoe last, depending on shape.
Kids' sizes and the 13C / 1Y jump
Kids' sizing in the US/UK has its own quirk. Toddler and preschool sizes are marked with a C (for child): 1C, 2C, 3C, all the way up to 13C. Then the numbering resets — the next size after 13C is 1Y (for youth), which continues up to about 7Y. A US 6Y kid's shoe is roughly equivalent to a US women's 7 or a US men's 5.5, which is why some adults with smaller feet end up shopping in the kids' department to save money.
In the EU and Japan, kids' sizes don't reset — they just continue on the same scale as adults. An EU 32 is an EU 32 whether it's on a child or a very small adult. JP 22 cm is JP 22 cm.
How to measure your foot at home
If you don't know your size in any system, measuring beats guessing. The Japanese system makes this easy because the size is your foot length in centimeters.
- Tape a piece of paper to a hard floor against a wall.
- Stand on it with your heel touching the wall, weight evenly distributed on both feet.
- Mark the tip of your longest toe — for many people that's the second toe, not the big toe.
- Measure from the wall edge of the paper to the mark, in centimeters.
- Repeat with your other foot. They'll typically differ by 0.5 to 1 cm.
That measurement, in cm, is your Japanese / Mondopoint size. Plug it into the converter and you get your starting point in US, UK, and EU.
Two things to keep in mind. First, measure in the late afternoon. Feet expand by 4–5% over the course of a day, and a morning measurement will run small. Second, always use the larger foot's size as your reference — a slightly loose shoe on the smaller foot beats a too-tight shoe on the larger foot.
Why brand size charts still matter
The Shoe Size Conversion tool gives you the conventional starting point. It's accurate within about half a size for most brands — but every brand designs its lasts (the foot-shaped forms a shoe is built around) a little differently, and that's where the variation comes in.
A few patterns worth knowing. Nike running shoes commonly run about half a size small for the listed number. Converse Chuck Taylors run about half a size large. New Balance is famous for true-to-size accuracy and for publishing actual width-specific lasts (2A, B, D, 2E, 4E). Italian dress shoes tend to run narrower than American casual shoes at the same nominal size.
For a first-time order from a brand you haven't worn, two things help. Read user reviews looking for the phrases "runs small," "fits true to size," and "runs large" — they appear so often they function as ratings. And order from a retailer with free returns. Sizing on paper is approximate; sizing on your actual foot is the truth.
Related conversions
If you're switching between measurement systems for other things, the same logic applies — pick the system you know, look up the equivalent.
- Length Converter — meters, feet, inches, miles. Useful when a size chart only gives foot length in inches.
- Weight Converter — kilograms, pounds, stone, ounces. The other unit-system gap most people hit when shopping internationally.
- Shoe Size Converter — sister tool that adds the Australian system and outputs foot length in mm/cm/inches alongside the four major systems.
- Bra Size Calculator — the other category of clothing sizing that's completely incompatible across countries.
Frequently asked questions
Why is there no formula — just a table?
Because shoe sizing isn't actually mathematical. US sizes are based on the Brannock device from 1925, UK uses a similar measure with an offset, EU uses the Paris point (each size equals two-thirds of a centimeter), and Japan uses real centimeters of foot length. The conversions between them are empirical mappings — what shoe makers and retailers have agreed corresponds to what — rather than equations you can derive. The tool reads from the standard reference table published in every shoe-industry handbook.
Why do men's and women's sizes use different scales?
Historical accident. Women's shoe sizing emerged around 1900 in the US with a 1.5-size offset from men's, so a women's 9 is roughly the same foot length as a men's 7.5. This offset persists in US and UK sizing. The EU and Japanese systems were standardized later and skipped the gendered split entirely — a 42 is a 42, regardless. The shoe's last shape might differ between men's and women's models, but the numerical size doesn't.
How accurate is the conversion?
Within about half a size for most brands. The starting point is the standard industry chart, but actual fit varies brand by brand because of how each maker designs its last. Italian-made shoes tend to run narrower than American ones. Athletic shoes typically run roomier than dress shoes. For a first-time order from a new brand, check brand-specific size charts and user reviews. If you're between two sizes, ordering both and returning one is sometimes worth the shipping.
What's Mondopoint exactly?
ISO 9407 — the international standard that defines shoe size as foot length in millimeters. A 270 mondopoint shoe is built on a 270 mm foot length. The Japanese system is essentially Mondopoint divided by 10 (so JP 27 = 270 mondopoint = 27 cm). You'll see actual Mondopoint sizes on military boots, ski boots, and some technical footwear. It's the most precise system but ignores foot width.
What's the difference between toddler (C) and youth (Y) sizes?
C stands for child — toddler and preschool sizes, roughly US 1C through 13C. Y stands for youth — older kids and preteens, US 1Y through 7Y. Confusingly, after US 13C the numbering resets to 1Y rather than continuing to 14C. A US 6Y youth size is roughly a women's 7 or a men's 5.5, which is why some smaller-footed adults buy youth shoes to get the same model at a lower price.
Why do EU sizes sometimes have decimals?
Because the underlying unit (the Paris point) is two-thirds of a centimeter, and the gap between two US sizes doesn't always land exactly on a whole Paris point. Italian and French manufacturers commonly stock half-point sizes like EU 40.5 and 42.5. German and Spanish brands usually round to whole numbers. Online retailers often list both for international compatibility.
What about width sizes — AA, B, D, EE, EEE?
This tool handles length only. Width is an independent dimension. US width sizes run from AAA (narrowest) through D (men's standard) to EEEE (widest). For women, B is standard, AA is narrow, D is wide. UK and EU widths exist but are less standardized. For accurate width sizing, measure your foot at its widest point and compare to brand-specific width charts — New Balance, Brooks, and Allen Edmonds publish full grids.
Do these conversions work for hiking boots and dress shoes too?
Yes for the numerical conversion, but the fit recommendation changes. Hiking boots and winter boots are commonly worn with thicker socks and benefit from half a size up for layering. Dress shoes are usually fit snug because leather stretches over the first dozen wears. Running shoes are often fit half a size large to leave thumb-width room ahead of the longest toe for downhill running. The conversion table gives you the right number; the right fit depends on the shoe's purpose.