Sizing Standards

ISO 216 defines the international standard for paper sizes, based on the square root of 2 aspect ratio (√2 ≈ 1.4142). This ensures that when a sheet is folded in half, the resulting piece maintains the same proportions.

ISO 9407 defines the Mondopoint system, which expresses shoe sizes in millimeters of foot length and width. It is used in Japan, Korea, Russia, and by many military and safety footwear standards. Most consumer shoe markets use derivative systems (EU, US, UK) that can be converted back to Mondopoint.

ASTM International (formerly the American Society for Testing and Materials) publishes the primary standards for clothing sizes in the United States. Key standards include ASTM D5585 (women's wear), ASTM D6240 (men's wear), and ASTM D6192 (children's wear).

US clothing sizes use a numerical system (XS, S, M, L, XL, or numeric 0–18 for women, 28–44 for men's waist) based on body measurements in inches. Our tools convert these to European (EN 13402), UK, and other regional systems.

EN 13402 is the European standard for size labeling of clothing, based on body measurements in centimeters. It replaced the older national standards across EU member states. The system uses primary dimensions (bust, waist, hip, height) to define size categories.

A typical European women's size 38 corresponds roughly to US size 8/10 and UK size 12. Men's EU sizes correspond to chest or waist measurements in centimeters.

Japan uses a centimeter-based shoe sizing system (e.g., 26.0 cm, 26.5 cm) that directly measures foot length. This is one of the most intuitive systems globally, closely aligned with the Mondopoint standard. Japanese sizes are the same for men and women — only the width designator (2E, 3E, 4E) changes.

Ring sizes vary significantly by region. The US/Canada system uses numbers 1–13 based on inner circumference in units of 1/16 of an inch. The UK/Australia system uses letters (A–Z+). Europe uses inner circumference in millimeters. Japan uses a numeric scale similar to the US but offset.