What Does OS Mean in Size for Clothing?

Discover the modern meaning of OS in clothing sizes, its origins, and how it applies to online shoppers in search of the latest apparel with Kiwi Sizing.
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Team Kiwi Sizing

Last updated on December 11, 2023

OS is an abbreviation for one size in most cases. But many shoppers may wonder: What does OS mean in size measurements specifically? And does it always refer to the same size?

The two letters are a common fixture on many clothing labels. The code indicates that an item, whether a shirt, pair of pants, or socks, is suitable for many people across a range of specific sizes or proportions. 

While commonplace these days, OS sizing is a relatively new development in the world of fashion. Though it can have drawbacks, the sizing scheme also offers benefits to clothing retailers, particularly those who do a lot of business online. 

The Surprising History of Clothing Sizes

What Does OS Mean in Clothing Sizes?

For many years, tailors designed and created clothing to the exact proportions of the wearer to ensure the perfect fit. World events altered this approach, as large numbers of soldiers going off to war required uniforms quickly. This led to the development of a universal system based on chest proportions. 

As the universal system made its way to civilian attire, some countries used specific size codes on the label of garments, including:


      • SW

      • W

      • SSW

      • SOS

      • XOS

      • XSSW

    OS appeared on labels along with other codes, although it had a different meaning. In the past, OS stood for outsized, which meant that an item of clothing was larger than the standard form. As for what OS means today, the definition of the code is far different in the modern clothing industry. 

    OS Means a Size Suitable for Many Individuals

    In some cases, OS may stand for overall size, but the definition remains the same. Products labeled with OS should suit many diverse body types and sizes. This makes it easier for people to purchase goods, especially when it comes to things like socks and stockings. 

    Variations on OS Size Labels

    Developing a truly universal sizing system is not always feasible when you consider the diverse range of body types and sizes. That’s why some clothing packaging will specify a size range in addition to the OS code.

    When a size range appears alongside OS on labels, that means people falling within that range should find the product to be a good fit. 

    For example, packaging for socks may have a shoe size range of 5 through 10. This indicates people who commonly wear those shoe sizes are likely to fit that pair of socks. 

    Benefits of OS Sizing on Garments

    Depositphotos 214935916 S

    While not always perfect, OS sizing is often useful when it comes to meeting customer needs and encouraging sales. When shoppers can easily determine whether a garment is suitable for their size, they’re more likely to make a purchase. 

    OS sizes are especially helpful for online shoppers. Because customers purchasing attire online can’t try on items before buying them, an item with an OS label offers extra reassurance. In the absence of this general label, online retailers can offer accurate size charts to ensure that shoppers are fully satisfied with their purchases. 

    Easy, Accurate Sizing for All

    Now you know what OS means in clothing size charts. Easy, efficient sizing is a must for shoppers, and Kiwi Sizing ensures your customers can accurately determine their size when purchasing clothing online.

    Our size charts are easy to use and offer a range of customization options to best suit your business. Contact us today for more information on our sizing tools and how they work. 

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