Why an EU Size Label Fit Differently Than Expected
EU sizing is often based more directly on specific body measurements (in centimeters) than US or UK numbered sizing, and different brands can interpret that measurement-based standard with varying amounts of ease (extra room built into the garment) — meaning a converted EU size, while numerically correct according to a standard chart, can still fit noticeably differently than expected due to brand-specific cut and ease differences.
This is the clothing-specific version of the same brand-fit-variation issue covered for shoes, and it's worth understanding the additional layer EU sizing's measurement basis adds.
How EU sizing's measurement basis differs from US/UK numbering
US and UK clothing sizes are more arbitrary numbering conventions (size 8, size 12) tied loosely to a general size range, while EU sizing is often more directly and explicitly tied to specific body measurements in centimeters — this closer tie to actual measurements can make EU sizing feel more precise, but doesn't eliminate brand-specific interpretation of exactly how much ease or room to build into a garment at that measurement.
Why brand-specific cut still causes fit variation
Even with a measurement-based standard, two brands' garments at the same labeled EU size can differ in cut, fabric stretch, and intended fit style (slim versus relaxed) — factors the size number alone doesn't capture, similar to how shoe lasts vary between brands despite a shared size number.
A practical approach
Checking a specific brand's own size chart and measurement guide (when available), rather than relying purely on a general size conversion chart, accounts for brand-specific cut differences that a universal conversion can't fully capture.