Why clothing sizes still don't mean the same thing from one brand to another

Audio By Carbonatix

Walk into three stores looking for a size 8, and you may leave with a 6, an 8, and a 10, all of which fit. Online, where shoppers cannot try garments on first, those discrepancies become harder to navigate.

When shopping across apparel brands, including online, consulting brand-specific sizing information can help shoppers navigate differences in fit. A size label may look precise, but as online retailer Felina explains, dimensions and fit are not necessarily identical from one brand to the next.

Clothing Sizes Were Never as Standardized as They Seem

Ready-to-wear clothing created a need to put different bodies into repeatable sizing categories, but those categories were never universal.

A 1994 National Institute of Standards and Technology report noted that U.S. sizing standards relied on body-measurement data gathered by the Department of Agriculture in the late 1930s. Bodies, demographics, and clothing preferences have changed since. ASTM International now maintains multiple body-measurement standards for different apparel populations and figure types.

Manufacturers can still develop their own fit specifications, target customers, and pattern-grading approaches. No single sizing chart governs every garment.

What Is Vanity Sizing?

Vanity sizing generally means assigning a garment a smaller numerical size than its measurements might historically suggest.

A Journal of Consumer Psychology study found that smaller-sized labels could produce more positive self-related responses. A 2017 study of size charts from 54 American apparel retailers also found evidence of size variation and inflation in women's apparel.

But vanity sizing does not explain every discrepancy. Brands can define categories differently without deliberately misleading consumers, and there is no universal threshold for what qualifies as vanity sizing.

There Isn't One Universal Measurement Behind a “Medium” or “Size 8”

A size is a category, not a precise measurement. ASTM standards use body measurements as baselines while accounting for fabric, ease, styling, and fit.

Body measurements describe the wearer; garment measurements describe the clothing. The two need not be identical. International systems add complexity because sizes do not always translate neatly between countries, while individual brands may define identical labels differently.

Pattern-Making Changes: How the Same Size Fits

Pattern-makers determine proportions, including shoulder width, bust or chest room, rise, inseam, waist placement, hip room, sleeve length, leg opening, and overall length. Pattern grading creates different-sized patterns from a design.

Two pants intended for similar body measurements can fit differently if one has a higher rise or more hip room. Fit depends on proportions, not simply overall size.

Ease Explains Why Your Body Measurements Don't Match Your Clothes Exactly

Ease is additional space that allows movement or creates a silhouette. Cornell apparel research describes wearing and design ease as extra fabric for movement and the desired shape.

A fitted garment may have little ease; an oversized sweater has more. Stretch changes how much is necessary because the fabric itself accommodates movement. Apparel guidance similarly notes that ease varies with design and intended fit. Thus, garments designed for similar bodies can have very different finished measurements.

Fabric and Construction Can Change the Fit, Too

Stretch versus non-stretch material, knit versus woven construction, fabric weight, and recovery after stretching all affect fit. ASTM guidance identifies fabric type and ease as considerations when translating body measurements into apparel.

Seaming, lining, and structure also affect movement, while intended use matters: Outerwear needs room for layers. Stretch may accommodate a broader range of measurements than rigid fabric, but it does not guarantee fit.

Why Sizing Can Even Vary Within the Same Brand

A fitted dress, relaxed T-shirt, and structured blazer may use different pattern blocks, ease, and construction. Products can also involve different designers, fabrics, or manufacturing facilities, while brands may update specifications or fit standards as product lines and target customers change.

Fabric, styling, ease, and proportions all affect required dimensions, as reflected in ASTM apparel-sizing guidance. The same brand and size, therefore, need not produce identical fits.

Why Online Shopping Has Made Sizing Confusion More Visible

Online shopping did not create inconsistent sizing; it removed the fitting room as an immediate solution.

When shoppers encounter different brand charts, product-specific information becomes more important. Fabric composition, intended fit, and model measurements provide context, while reviews describing garments as running small, large, or true to size can reveal common experiences. Online shopping makes existing sizing differences more consequential because consumers often choose before trying garments on.

Why Size Charts Are More Useful Than the Number on the Tag

Treat a brand's size chart as a starting point, rather than assuming, “I'm always a medium.”

Check whether it lists body or garment measurements and follow the brand's measuring instructions. Compare the relevant garment category, fabric, and stretch; read fit descriptions; and consider model measurements and sizes when available. Above all, consider the intended fit instead of automatically ordering your usual size. Size charts are brand-specific tools, not universal conversion charts.

Why “True to Size” Isn't as Objective as It Sounds

“True to size” generally means a garment fits as someone expected based on previous purchases—not that it conforms to a universal size.

Body proportions and preferences also differ. The Cornell researchers found individuals had distinctive fit preferences, including different garment and sleeve lengths. Reviews provide useful context, but two shoppers can reasonably reach different conclusions about the same garment.

Will Clothing Sizes Ever Become Truly Standardized?

ASTM lists 15 active standards for body measurement and apparel sizing, covering populations from children to different adult figure types.

Universal sizing remains difficult because bodies vary in dimension, shape, and proportion; countries serve different populations; and garment categories require different ease and structure. Standard measurements must also coexist with changing designs and fit preferences.

Better body-measurement data, digital fitting technology, and detailed sizing tools may improve shopping, but cannot eliminate the challenge of translating varied bodies and clothing into a limited set of labels.

Stop Treating the Size Label as a Universal Measurement

A clothing size is shorthand, not an objective measurement shared across the industry. Vanity sizing contributes to variation, but so do pattern-making, ease, fabric, construction, and intended fit.

Consumers are better served by measurements and product-specific fit information than loyalty to a number. Especially online, understanding sizing can make shopping more informed and make moving up or down a size less personal. The label is ultimately just the category attached to the garment that fits.

This story was produced by Felina and reviewed and distributed by Stacker.