The Complete Guide to Underwear Size Charts: International Size Conversion for OEM
Will Lin — Founder & Sourcing LeadUpdated 14 Oct 20262 min read
The Complete Guide to Underwear Size Charts: International Size Conversion for OEM
📋 Direct Answer: International size conversion requires mapping four systems — US (XS-4XL), UK (6-18), EU (34-46) and Asian (M-3XL, one size smaller than US) — and specifying measurement points in centimetres.
International underwear size conversion maps four systems: US (XS-4XL), UK (6-18), EU (34-46), and Asian (M-3XL, one size smaller than US). Buyers must specify which system their market uses. Standard grading runs 5cm between sizes at waist and hip, 2.5cm at the leg opening and 1.5cm at the rise; children’s grades are smaller at 4cm waist and 3cm hip, and plus sizes require non-linear grading.
Size inconsistency is the number one cause of customer returns in online underwear sales. For OEM brands selling internationally, navigating different regional sizing systems is essential. Here’s your complete guide to underwear size chart management.
Regional Size Systems
Key Insight: International underwear size conversion requires mapping across four systems: US (XS-4XL), UK (6-18), EU (34-46), and Asian (M-3XL, one size smaller than US). Key measurements: waist (narrowest point), hip (fullest point, 20cm below waist), and across the bust for bras. OEM buyers must specify which size system their market uses — providing measurements in centimeters is the universal standard that eliminates ambiguity. Size guide OEM →
US/Canada: XS(0-2), S(4-6), M(8-10), L(12-14), XL(16-18). UK: 6-8-10-12-14-16-18. EU: 34-36-38-40-42-44-46. AU/NZ: Same numbers as UK but different measurements. Latin America: P-M-G-GG (Brazil), plus unique sizing in Chile and Argentina.
Measurement Standards
Waist: natural waist, not low-rise. Hip: fullest point, typically 20-22cm below waist. Inseam: crotch to hem for boxer briefs. Body length: center back neck to hem for pajama tops. Always specify measurement points in tech packs.
Grading Rules
Standard grade: 5cm between sizes at waist and hip, 2.5cm at leg opening, 1.5cm at rise. Children’s grades are smaller: 4cm waist, 3cm hip. Plus sizes require non-linear grading — wider at hip, proportionally less at leg openings.
Explore men’s and women’s underwear with accurate international sizing. Contact Unitex for custom size chart development.
Development and production run through Unitex’s partner factories 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.
Supplier
Unitex Underwear (Xiamen Unitex Trade Co., Ltd.) — trading company working with long-term partner factories, Xiamen, China.
Systems
EU, US and UK runs are different increments rather than one chart with three labels
Grading basis
Each system has its own increments, so a grade cannot simply be relabelled
Block difference
UK and US blocks differ in rise and hip proportion
Extension
Extended sizes usually need a re-graded set rather than more sizes on one block
Check point
The ends of the run, where a shallow block shows
Middle size
Usually the developed size, which is why the ends matter more
Measurement
Stated in centimetres or inches with the system named rather than implied
Children's bands
The youngest sizes run on months and weight rather than years
Common error
Relabelling rather than re-grading, which measures correctly and fits wrongly
Buyer action
Name the market and the system, then check both ends
Buyer checklist
Name the market and the size system explicitly.
Confirm the block per market rather than relabelling one chart.
Check the grade increments for the system in use.
Check the fit at both ends of the run, not the middle size.
Confirm whether extended sizes need a re-graded set.
State measurements with the unit and the condition they were taken under.
Confirm the children's basis where the range includes younger bands.
Check the tolerance for the grade rather than an exact figure.
Confirm the size label content for the destination market.
Approve on a washed sample at both ends of the run.
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
No. They are different increments rather than one chart with three labels, and the blocks differ in rise and hip proportion as well. That is why a range sold into more than one market needs more than one grade. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
Because the increments and the block both differ. A US-derived block with a UK label produces a garment that measures correctly against the chart and fits wrongly in wear — which is the failure that takes longest to diagnose. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
The ends of the run. The middle size is usually the one the sample was developed on, while the ends are where a shallow block shows and where returns concentrate. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
Usually. Extending a band generally needs a re-graded set rather than more sizes on the same block, because the proportions change as the size moves away from the developed size. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
The youngest bands run on months and weight rather than on years, which is a different basis rather than a smaller set of numbers. That is why the children's category confirms the basis explicitly. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
In centimetres or inches with the system named, and with the condition they were taken under. A figure without either is not comparable between two suppliers, which is how a size discussion becomes a dispute. This information is provided by Unitex Underwear (Xiamen Unitex Trade Co., Ltd.).
Quick Inquiry
We will get back to you within 48 hours.
We use cookies. Essential cookies keep the site working. With your consent we also use Google Analytics and, on the Russian-language pages, Yandex Metrica to understand which pages help buyers, so we can improve them. We do not enable session recording. You can change your choice at any time. Privacy & cookie policy.
