Measure once, convert everywhere
Every shoe numbering system is trying to describe the same thing — how long your foot is — but only one of them says so directly. Japanese sizes are the foot length in centimetres, so a shoe marked 26.0 is built for a 26.0 cm foot. US, UK and EU numbers are conventions layered on top of that, which is why they never line up neatly.
So the reliable order is: measure your foot in centimetres, then convert. Stand on paper with your heel against a wall, mark the tip of your longest toe, and measure from the wall to the mark. Do both feet and use the longer one — a 5 mm difference between feet is common and nobody notices until a shoe pinches. Measure in the evening, because feet swell over the day.
How the systems relate
- Japan — foot length in centimetres, in 0.5 cm steps. The most literal system there is.
- US men's — roughly the centimetre length minus 18. A 26.0 cm foot is about US 8, 27.0 cm is US 9.
- US women's — about 1.5 higher than men's for the same foot. That 26.0 cm foot is US 9.5 in women's numbering.
- UK — about one size below US men's, and about 2.5 below US women's. US 9 men's is UK 8; US 8 women's is UK 5.5.
- EU — roughly the centimetre length plus 15, rounded to the half size. A 26.0 cm foot is about EU 41.
The men's-to-women's gap is the one that catches people out. A shoe listed as women's US 9.5 and one listed as men's US 8 are close to the same physical shoe, which matters when a style you want is only stocked in the other department.
Why the same marked size fits differently
Internal length varies by 2 to 5 mm between brands at the same marked size, because the marking is a convention rather than a measurement. That is more variation than a half size in some ranges, which is why "I'm a US 9" is less useful information than it sounds.
The fix is to work in millimetres. Most brands publish their own size guide with a centimetre or insole-length column — match your measured foot against that instead of trusting the number on the box. Japanese and Korean brands make this easy since their sizing is already in centimetres and millimetres.
Women's clothing across US, UK, EU and Japan
Clothing has no equivalent of foot length to anchor it, so conversions are looser still. The rough alignment is that US and UK differ by four (US 4 is UK 8), and EU numbers run about 32 higher than US (US 4 is EU 36).
Japan uses 号 (gō), which does have a measurement behind it: the JIS standard sets 7号 at an 80 cm bust, 9号 at 83 cm, 11号 at 86 cm, adding about 3 cm every two sizes. 9号 is the Japanese standard size, chosen because a national survey put the average adult women's bust near 83 cm.
Be aware that American cuts generally run larger than Japanese and European ones at the same nominal conversion. If a Japanese listing gives a bust measurement, that number is worth more than the size label.
What this converter assumes
- Japan (shoes) = foot length in cm · US men's ≈ cm − 18 · US women's = US men's + 1.5
- UK ≈ US men's − 1, or US women's − 2.5 · EU ≈ cm + 15, rounded to the half size
- China (shoes) = (mm − 50) ÷ 5
- Japanese clothing 号 = JIS L 4005 bust sizing (7号 = 80 cm, +3 cm per 2 sizes)
- All cross-country clothing mappings are approximate — brand variation exceeds system variation
Frequently asked questions
How do I convert my US shoe size to UK?
For men, UK is one size below US — US 9 is UK 8. For women the gap is larger: UK is about 2.5 below US, so US 8 is UK 5.5. This is why the same physical shoe carries different numbers on each side of the Atlantic, and why converting between men's and women's listings needs care.
What is my size in Japanese sizing?
Japanese shoe sizes are simply the foot length in centimetres, so a 26.0 label means a 26.0 cm foot. That makes Japan the easiest system to convert into — measure your foot in centimetres and you have the number. US men's is roughly cm minus 18, so 26.0 cm is about US 8.
How do I measure my foot length?
Stand on a sheet of paper with your heel against a wall, mark the tip of your longest toe, and measure from the wall to the mark. Do both feet and use the longer one — a 5 mm difference between feet is common. Measure in the evening, since feet swell during the day.
Why does the same US 8 fit differently across brands?
Because the label is a convention, not a measurement. Internal length varies by 2 to 5 mm between brands at the same marked size. Work from your foot length in centimetres and check the brand's own size guide, which usually lists cm or insole length — that removes one layer of guessing.
What does a Japanese clothing size like 9号 mean?
It is a bust measurement in the JIS standard: 7号 is 80 cm, 9号 is 83 cm, 11号 is 86 cm, and each two sizes adds about 3 cm. 9号 is the Japanese standard size. Roughly it maps to US 4 and UK 8, but Japanese cuts run smaller than American ones, so check the listed measurements.
Can I order from this table alone?
Treat it as a shortlist, not a decision. Numbering systems differ by country and brands differ from each other by more than the systems do. Narrow it down here, then match against the actual measurements on the product page — especially for international orders where returns are expensive.