Composition of the European sizing standard system:

The overarching body is CEN (Comité Européen de Normalisation). It develops and maintains the EN 13402 standard, which is the official "composition" of the European sizing system.
EN 13402 is titled "Size designation of clothes". Its goal is to create a unambiguous, consumer-friendly system based on body dimensions, replacing the old national systems (like French, Italian, or German sizes).

EN 13402 is not a single chart but a framework with multiple parts, each defining a different way to designate size.
Part EN 13402-1: Terms, definitions, and body measurement procedure. Description: The foundation. It defines exactly how and where to measure the human body (e.g., chest girth, waist girth, hip girth, height, inside leg). Standardizes posture, tape tension, and landmark points.
Part EN 13402-2: Primary and secondary dimensions. Description: Defines the primary size designation we see most often (e.g., "92-76-96"). It lists combinations of body measurements that correspond to a "body type."
Part EN 13402-3: Size intervals, body measurements, and pictograms. Description: This part translates the precise measurements from Part 2 into simplified, convenient size codes (like 38, M, or 175/92A). It defines the size intervals and the associated pictograms.
Part EN 13402-4: Coding system. Description: A technical standard for machine-readable codes (like barcodes or RFID tags) that can contain the full set of body measurements from Part 2.

Body Dimension Tables: Statistical tables (based on extensive anthropometric surveys of the European population) that define which combinations of measurements are most common. This ensures sizes fit real body shapes.
Pictograms: Standardized symbols that indicate. Fit: (e.g., slim, regular, loose), Body Shape: (e.g., for bras: breast shape; for pants: seat shape).
The "Chest-Based" Number for Men: The common men's size (46, 48, 50) is simply the chest circumference in cm, divided by 2 (e.g., a 100 cm chest ≈ size 50).
The "Calculated" Number for Women: The common women's size (38, 40, 42) is approximately half the bust circumference (e.g., a 88 cm bust ≈ size 44, but often scaled to match historic sizes).

Footwear uses the "Paris Point" system, defined by ISO 9407 (aligned with EU standards).
Formula: EU Shoe Size = (Foot length in cm + 2) * 1.5.
The "+2" accounts for a basic toe allowance.

This is the most important part of the "composition" to understand:
The system is a standard, not a law. While EU legislation encourages its use for consumer protection, adoption by brands is voluntary and inconsistent.
The "Composition" is in the Label: The ideal EN 13402 label includes the size number, a pictogram for fit, and the key body measurements in cm—giving you all three parts of the system at once.