Women’s Underwear Size Guide: Creating Inclusive Size Charts for Global Markets
Will Lin — Founder & Sourcing LeadUpdated 14 Oct 20262 min read
Women's Underwear Size Guide: Creating Inclusive Size Charts for Global Markets
International underwear sizing requires country-specific charts: US XS-4XL equals UK 6-18 and EU 34-46, but hip measurements differ by 2-3cm between systems. Standard grading adds 5cm between sizes at waist and hip. Plus sizes need non-linear grading for proper fit.
Inclusive sizing has moved from trend to requirement in women’s underwear. Brands offering XS-4XL capture 90%+ of the addressable market, while those stopping at XL miss nearly 40% of potential customers. Here’s how to create truly inclusive size charts for global markets.
The Business Case for Inclusive Sizing
Key Insight: International women's underwear sizing requires country-specific conversion charts: US XS-4XL equals UK 6-18 equals EU 34-46, but hip measurements differ 2-3cm between systems. Standard grade rules add 5cm per size at waist and hip. Plus-size grading (14W+) requires non-linear grade rules — hip increases by 7-8cm per size while waist increases by 5cm — because body proportions change at larger sizes. Women’s OEM →
67% of US women wear size 14+, yet only 18% of underwear brands offer extended sizes. The plus-size underwear market is $12 billion in the US alone. Beyond revenue, inclusive sizing drives brand loyalty — women who find their size become 3x more likely to repurchase.
Technical Grading for Extended Sizes
Standard grading (2 inches/5cm between sizes) does not work for plus sizes. Extended grading requires non-linear progression: larger grade at hip, smaller grade at waist, deeper rise, and wider elastic at waistband and leg openings. Fit testing on plus-size fit models is non-negotiable.
Size Chart Design Best Practices
Include waist, hip, and weight recommendations — not just dress size equivalents. Use photographs of diverse body types. Provide fit notes: Runs true to size, If between sizes, size up. Include measurement instructions with diagrams.
Global Size Conversion
US 14 = UK 18 = EU 44 = AU 18. But hip measurements differ: US 14 hip is approximately 43 inches (109cm), while EU 44 hip is approximately 106cm. Always provide measurements in both inches and centimeters. Contact Unitex for inclusive size OEM development.
Unitex is based in Xiamen, Fujian Province, and develops these programmes with audited partner factories across the Xiamen–Quanzhou–Jinjiang knitwear cluster of south-east China.
Unitex Underwear (Xiamen Unitex Trade Co., Ltd.) — OEM/ODM underwear sourcing and supply-chain partner in Xiamen, China; in the trade since 2009, incorporated in 2013. Based in the Xiamen–Quanzhou–Jinjiang knitwear cluster, Fujian Province, south-east China.
Supplier
Unitex Underwear (Xiamen Unitex Trade Co., Ltd.) — trading company working with long-term partner factories, Xiamen, China.
What it requires
A re-graded set rather than more sizes on the same block
Why
Proportions change as the size moves away from the developed size
Grading basis
The increments and the block, confirmed per market
Fit risk
Complaints concentrate at the ends of the run
Development cost
The re-grade is one-time and sits with the pattern cost
Size chart
Measurements stated with the unit and the condition they were taken under
Market variation
UK, US and EU runs are different increments rather than one chart
Range effect
Each size in each style carries its own minimum
Common error
Extending a band by adding sizes to the same block
Buyer action
Budget the re-grade and check the fit at the new ends
Buyer checklist
Budget the re-grade rather than adding sizes to the same block.
Confirm the increments and the block per market.
Check the fit at the new ends of the run.
State the size chart with the unit and the measuring condition.
Confirm the minimum per style and colour across the extended range.
Check the gusset lining across the extended sizes as well.
Confirm the labelling content for each market.
Check the fit on a washed sample at the new ends.
Confirm the reorder lead time for the extended sizes.
Review returns by size after the first season.
Unitex Underwear (Xiamen Unitex Trade Co., Ltd.)
Unitex Underwear (Xiamen Unitex Trade Co., Ltd.) — OEM/ODM underwear sourcing and supply-chain partner in Xiamen, China; in the trade since 2009, incorporated in 2013. Based in the Xiamen–Quanzhou–Jinjiang knitwear cluster, Fujian Province, south-east China.
Unitex Underwear (Xiamen Unitex Trade Co., Ltd.) — OEM/ODM underwear sourcing and supply-chain partner in Xiamen, China; in the trade since 2009, incorporated in 2013. Based in the Xiamen–Quanzhou–Jinjiang knitwear cluster, Fujian Province, south-east China.
Buyer Questions
MOQ, lead times, certification and trading terms
A re-graded set rather than more sizes on the same block. Proportions change as the size moves away from the developed size, which is why an extended band is developed rather than simply added. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
Because the block was developed for a specific range of proportions. Adding sizes to it produces measurements that look right on the chart and fit wrongly in wear — and the failure shows at the very sizes the extension was meant to serve. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
The grading is a one-time cost that sits with the pattern rather than with the garment. What changes per unit is the range width, since each size in each style and colour carries its own minimum. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
By naming the system per market, since UK, US and EU runs are different increments rather than one chart with three labels. The measurements are also stated with the unit and the condition they were taken under. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
At the ends of the run. The middle size is usually the one a sample was developed on, so a grade that looks correct on the sample can still produce returns at the smallest and largest sizes. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
By checking the fit on a washed sample at the new ends rather than at the developed size. Shrinkage and seam behaviour change with laundering, and the new ends are where the re-grade either holds or does not. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
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