Why Clothing Sizes Differ by Brand

Vanity sizing refers to the practice of labeling a garment with a smaller size number than older standards would dictate, so the customer feels good about fitting into a 'smaller' size. Research has shown that shoppers are more likely to purchase and have higher satisfaction with clothing labeled at their perceived ideal size.

The effect has been documented over decades: a 'size 8' garment in the US today has significantly larger measurements than a 'size 8' from the 1970s. Studies have found that what was a size 16 in 1958 would be labeled a size 8 or smaller today. Vanity sizing has inflated US women's size numbers across the board.

Different countries developed their sizing standards independently. EU sizing is based on body measurements in centimeters; US sizing is based on an evolving set of informal conventions; Japanese sizing reflects the body proportions of the Japanese population at the time the standards were set.

Because Japanese women historically have had different average proportions from US or European women, Japanese standard sizes are cut narrower and shorter. A Japanese size M may correspond to a US XS. This is not about quality or preference — it is about which population the brand was originally designed to serve.

Even within the same country, brands choose their own 'fit model' — the body proportions they design their base size around. A brand targeting petite customers uses a smaller fit model. A brand targeting athletic builds uses a different one. Since the brand only needs to ensure consistency within its own line, not across the industry, sizes differ.

Premium brands and designer labels sometimes deliberately cut smaller, creating an aspirational fit — wearing a size 4 from a luxury brand feels more exclusive than a size 8 from the same label. Budget and fast-fashion brands often size generously to minimize returns.