Why Your T-Shirt Size Isn't the Same in Every Brand

You've felt it before: a Medium from one brand fits perfectly, a Medium from another is snug across the chest, and a Medium from a third practically swims on you. Sizes aren't broken — but they also aren't standardized. Here's what's actually going on.

There's no single "Medium"

Unlike shoe sizing (which is based on measurable foot length) or ring sizing (based on a physical diameter), letter-based clothing sizes like S/M/L are not tied to any single agreed-upon measurement standard. Every brand designs its own size chart from scratch, based on its own target customer and its own design decisions. A "Medium" is simply whatever a given brand decided that label should mean.

The "block pattern" is the real culprit

Behind every garment is a block pattern — the base template a brand's designers use to build every style in a given category. Two brands making a "regular fit" t-shirt might both call it Medium, but if their block patterns were drafted around different body proportions, the actual chest, length and shoulder measurements behind that label can differ by an inch or more.

"Ease" changes everything

Ease is the extra room a garment includes beyond your actual body measurement, and it's a deliberate design choice, not a mistake. A brand aiming for a slim, fitted silhouette builds in less ease; a brand going for a relaxed, boxy look builds in more — even if both start from a similar base measurement. This is why "size Medium" from a slim-fit streetwear brand and "size Medium" from a classic relaxed-fit brand can differ noticeably, despite sharing a label.

Regional sizing conventions differ too

On top of brand-specific block patterns, sizing conventions vary by region. US, UK, EU and Asian size charts don't map onto each other with simple conversions — an EU size label and a US size label for what's nominally "the same size" can correspond to different actual measurements, which is exactly why cross-region shopping causes so much sizing confusion.

What actually works: measure once, compare charts

Because letter sizes aren't standardized, the only reliable method is to measure your actual body (chest, shoulders, length preference) and compare that number against each brand's own published size chart — not against the size label you usually wear elsewhere. It takes two extra minutes and avoids the guesswork entirely.

Have your chest measurement? Use the T-Shirt Size Calculator →