Size Conversion Methodology

Every size on this site is produced by one conversion function reading from a single measured base: foot length in millimetres for shoes, bust or chest in centimetres for clothing, and inner circumference in millimetres for rings. Each regional size is a rule applied to that base, not a number copied from another chart, so the columns cannot drift out of step with one another.

Standards behind the shoe tables

Shoe sizes start from foot length, and the conversions follow the published standards that define each system:

• ISO 19407:2023, Footwear, Sizing, Conversion of sizing systems sets the cross-system tables for Mondopoint, European, UK, US, China, Japan and Korea, all keyed to foot length. It is the first full edition and replaced the earlier ISO/TS 19407:2015.
• ISO 9407:2019, Footwear sizing, Mondopoint system defines the centimetre or Mondopoint mark from foot length and width in millimetres. It is the second edition and replaced ISO 9407:1991.
• JIS S 5037:1998 defines Japanese sizing as foot length in centimetres at half-centimetre steps, with girth grades A to G in separate men's, women's and children's tables.
• GOST 11373-88 sets the post-Soviet metric size as foot length in millimetres at a 5 mm step, the number still stamped inside East European shoes.
• GB/T 43293-2022, in force since May 2023, is the current Chinese shoe-size standard on the Mondopoint millimetre base, replacing GB/T 3293.1-1998.

US numbers follow the Brannock device, which offsets the men's and women's scales by one full size for the same foot length. EU numbers count in Paris points of two thirds of a centimetre, measured from the last rather than the foot, which is why EU-to-centimetre tables from different makers disagree by a few millimetres.

Standards behind the clothing tables

Clothing sizes describe the body, so the conversions rest on body-measurement standards rather than garment dimensions:

• EN 13402, Size designation of clothes (Parts 1 to 3) is the European body-measurement system. Part 3:2017 lists body dimensions and intervals and states plainly that garment dimensions are not part of the standard, which is why one body can carry a DE, FR and IT number that never match.
• ASTM D5585-21 gives the US body-measurement tables for the adult female misses figure, sizes 00 to 20.
• GB/T 1335.1 and GB/T 1335.2 (2008 editions, in force since 2009) set the Chinese men's and women's sizes on a height-and-bust format such as 170/92B.
• JIS L 4005 defines Japanese women's garment sizes using the numbered gou system tied to bust and height.

Standards behind the ring tables

• ISO 8653:2016, Jewellery, Ring-sizes defines the size as the inner circumference of the ring in millimetres, which is the same number Continental Europe prints on the band. US uses a numbered scale in half steps, and the UK uses a single alphabetical run that reaches Z and then the extended codes Z1 and Z2.

Where conversions break

Conversion is not always exact, and the site shows this rather than hiding it. Where a size has no exact match in another system, the closest equivalent is shown; where a foot or body falls between two standard sizes, the page says so and gives a measurement range instead of a single number.

How the data stays consistent

Every figure comes from the single conversion function described above, so the tables are internally consistent by construction rather than by manual review. Each standard is named here with its edition, so any reader can check a conversion against its source. When a reader reports a mismatch, the relevant rule is corrected once and every affected page updates together.

Limits

Brand sizing varies from any standard chart, vintage and specialty items often use their own grading, and these tables are guidance rather than a guaranteed fit. When a size sits on a boundary, measure the foot, finger or body and check the specific brand's chart before buying.

Report an issue

Found a number that looks wrong? Email the details to hello@convertsizes.com and name the page, and the underlying rule will be checked against the standard it follows.

These charts are maintained by the ConvertSizes data team, who build every table from the published sizing standard it follows and reconcile it whenever a reader reports a mismatch. The project is independent of any shoe, clothing or jewellery brand, so the numbers answer to the standards rather than to a catalogue. Corrections and questions reach the team at hello@convertsizes.com.