Why clothing sizes differ between brands and countries
A size 10 has no fixed meaning. Standards that describe body measurements exist in Europe, the United States and internationally, but none of them obliges a brand to use particular numbers.
Last updated: September 28, 2026
Sizes are names, not measurements
A size number or letter tells you where a garment sits in the range of one brand. Which body it is made for is the decision of that brand. Two retailers we compared both sell a UK 10, one for hips of 93.5 cm and one for hips of about 95 cm.
Waist sizes in inches look like measurements but are not reliable either. When a Canadian broadcaster had jeans measured in 2022, most waistbands were larger than their label.
The international approach: label the body
The international standard ISO 8559 and the European standard EN 13402 take a different route. They designate a garment by the body dimensions it is made for, in centimetres. For a man’s jacket the primary dimension is the chest girth; further dimensions such as waist girth and height can be added.
EN 13402 describes a label with a small figure, a pictogram, on which the body dimensions are printed. If you see such a label, compare its numbers with your own measurements and ignore the size name.
Both standards are voluntary. They describe how to measure and how to label; they do not fix which sizes a brand must offer.
The United States: from government standard to voluntary tables
According to a report of the National Institute of Standards and Technology, its predecessor compiled the first standard body dimensions for clothing in the 1950s. The Department of Commerce withdrew these voluntary standards in 1983, and the standards organisation ASTM took over the subject.
ASTM publishes tables of body measurements, for example for women of the misses figure type in sizes 00 to 20 and for men by chest size from 34 to 52. They are voluntary as well, and sold as documents.
What this means when you shop
- Take your body measurements once and keep them.
- Open the size chart of the brand, not a general conversion chart.
- Choose the size by measurement. Use conversion charts only to translate a label from another country.
- Check the return conditions before ordering from abroad.
Worked example: two labels, one garment size
A dress carries the label EU 38. In the charts we checked, one retailer prints EU 38 for UK 10 and another prints EU 36 for the same UK 10. The first uses the French number under the name EU, the second the German number.
A second number on the label settles it. If the label also says IT 42 or UK 10, the 38 is French. If it says IT 44 or UK 12, the 38 is German.
Common mistakes
- Believing that a standard size exists and one brand is simply wrong.
- Comparing sizes between brands instead of comparing measurements.
- Treating letter sizes such as S, M and L as international. Each brand assigns them itself.
- Treating the label EU as one scale.
Sources and checks
Statements about standards rest on their catalogue entries and official previews; the full texts are sold by the standards bodies and were not read. Last checked against the sources on September 28, 2026.
Used for: designation by body dimensions in centimetres, and chest girth as the primary dimension of a man’s jacket.
Used for: size labelling based on body measurements with a standard pictogram.
Used for: the first standard body dimensions in the 1950s, the withdrawal in 1983 and the role of ASTM.
Used for: the titles and size ranges of the current US tables of body measurements.
- ASOS, women's dresses size chart
- Marks & Spencer, size guide
- John Lewis, international size conversion
- Next, international size guide for the Oasis brand
Used for: the body measurements stated for UK 10, the numbers printed under the label EU and the letter sizes printed next to UK numbers.
Used for: measured waistbands compared with their labels.
Frequently asked questions
- Is there an official standard for clothing sizes?
- There are standards for how to measure the body and how to label clothes, such as ISO 8559 and EN 13402, and tables of body measurements from ASTM. All are voluntary. None fixes what a size 10 or a medium is.
- What is vanity sizing?
- The practice of putting a smaller size on a garment than its measurements suggest. Measurements of jeans in 2022 found most waistbands larger than their labels.
- Are S, M and L the same everywhere?
- No. Letter sizes are assigned by each brand. In one retailer chart we checked, M covers both UK 10 and UK 12.
- What is the pictogram on some European labels?
- A small figure with body dimensions in centimetres, as described in the European standard EN 13402. It tells you which body the garment is made for.