Fashion Sizing Is Made Up, and the Industry Is Fine With That. Are We?

A size 12 in Zara is not the same as a size 12 in M&S, H&M, ASOS, Next, or anywhere else. Some of us have found that out the hard way. There is no agreed definition of a size 12. Every brand uses its own measurements, fit model, and grading system, which means the same person can walk into three different shops and leave with three different sizes. The reasonable conclusion is that the fashion sizing system is a mess. The conclusion many people reach instead is that something is wrong with their body.

That gap between what the evidence says and what people feel is where the harm sits. Numbers on clothing labels carry far more weight than they have any right to, given that they are essentially made up. Most of us know that sizes vary between brands, yet the number can still hit immediately in a changing room. It is enough to make us start second-guessing our bodies. A label that reads larger than expected can derail a shopping trip and a significant portion of the day attached to it. That is a lot of power to hand to a figure with no consistent meaning.

Where Did Fashion Sizing Even Come From?

Clothing sizes were invented to solve a manufacturing problem. Once factories began making clothes in bulk in the early 20th century, they needed a shorthand that removed the need to measure every customer individually.

Before that, clothes were largely made to measure. After mass production, bodies were expected to fit predetermined categories. That was a significant shift in logic, but the industry never spent much time examining its consequences. The US government tried to make sizing consistent in 1939, when the Department of Agriculture measured around 15,000 women across the country at 58 points on the body in an attempt to establish a standard system. The data was a mess from the start. The sample skewed towards younger white women, the measurements varied widely, and no reliable universal standard emerged.

The result was a sizing framework that brands were advised to use, but most ignored because it was never mandatory. In 1983, the government withdrew the standard altogether. At that point, there was no official women’s sizing system in the US, only whatever each brand chose to use.

Instead of letting the number stay meaningless, the fashion industry spent the post-war decades loading it with more significance. As fashion became increasingly tied to aspiration and status, the size label quietly became a social verdict. A smaller size became cultural shorthand for discipline and desirability. The industry continued to present one body type as the ideal, and the size associated with that body became the target. A size 16 was a standard model size in the 1940s. By the 1960s, that had shifted to a size 12.

Vanity sizing makes this worse in a very specific way. Brands that run their sizes deliberately small are creating a system in which customers feel they have failed before they have even tried anything on. Brands that run large attempt to flatter customers into associating the brand with the "positive" feeling of having gone down a size. (Notice the underlying assumption: "smaller = better", stated implicitly.) Either way, the customer is navigating a number chosen for reasons that have little to do with consistent measurement.

The strange part is how thoroughly this has become the customer’s problem to manage. Shoppers are expected to know their size in every brand, absorb the experience of being a different number depending on where they are standing, and accept all of it as a normal part of buying clothes. When nothing fits and the changing room becomes something to dread, the body is treated as the variable. In reality, the sizing is.

There is a straightforward fix the industry has consistently declined to make: display standardised garment measurements alongside the size label, so customers can check whether something is likely to fit rather than guessing from a number that changes meaning from one brand to the next. Some brands do this, but most do not. The cost is carried by the customer, both in fitting rooms and in how they feel about their body long after they have left the shop.

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Index:MH sets measurable standards for how the beauty and fashion industry affects consumer mental health. To find out more about our work, visit indexmh.org.