International Size and Unit Conversion for Marketplaces
How to convert sizes and units for US, EU and Gulf marketplaces using each product's own size list, so fewer orders come back as costly returns.
International size and unit conversion means listing the product you sell at home as "M" or "38" in the size and units a buyer in the US, Europe or the Gulf actually understands. There is only one reliable way to do it: not a generic chart, but a conversion defined on each product's own size list, because the same "M" means different measurements at two different brands. That is why Bulutegra converts sizes on US orders one step up according to the product's own size list rather than applying a fixed formula. This article explains how to set up size and unit conversion without pushing your return rate up.
Why sizes drift between countries
A size is a label, not a standard. Women's clothing runs 36-38-40 in Turkey and most of Europe, 8-10-12 in the UK and 4-6-8 in the US; letter sizes (S, M, L) depend entirely on each brand's pattern. In footwear, EU 40 maps to one number for US women and a different one for US men. Children's clothing uses age, height and weight systems side by side.
Fit expectations complicate it further. In the US market many brands expect the same label to fit a broader body; what a Turkish or Italian maker calls "L" often feels like "M" to an American buyer. The result is a return with the reason "too tight". In cross-border selling a return is not just a lost sale but two international shipments and customs handling; we break down that cost in marketplace returns and the customer return portal.
The goal of size conversion is not "finding the right chart". It is making sure the product that reaches the buyer fits the way they expected.
The one reliable approach: the product's own size list
Generic conversion charts (EU 38 equals US 8, and so on) are where you start, not where you finish. The correct structure is this: every product's master record holds its own ordered size list (XS-S-M-L-XL, or 36-38-40-42-44), and the conversion rule operates on that list. A "one size up for the US" rule moves to the next size in the list; it never jumps to a size the product does not have. A four-size product does not lose its largest size in the US, and its smallest does not disappear.
In Bulutegra, sizes on US orders are converted one step up according to the product's own size list. When a US buyer selects "M", the line item that reaches your warehouse is your "L"; the order lands in the ERP that way, so the warehouse never picks the wrong size. Because the rule reads from the product's list, letter-sized and number-sized products convert with the same logic but within their own sequence. No shift is applied for Europe and other markets; there, listing accuracy and the size chart do the work.
Units: centimetres, inches, grams, pounds
Units are a separate issue from sizes. The US and some other markets use inches for length and pounds and ounces for weight; Europe, the Gulf and Russia use centimetres and grams. If dimensions on Amazon.com are not in inches, the buyer cannot read the listing; the same content on Amazon.de must be in centimetres. When listing:
- Keep measurements in one unit on the product card (centimetres and grams) and convert per channel.
- Round consistently; do not show 92 cm as 36.2 inches on one channel and 36 inches on another.
- Do not confuse package dimensions with product dimensions; shipping cost is driven by the package.
- For footwear, add insole length in centimetres; it is the most reliable data point, independent of the size label.
Unit conversion is inseparable from content production; the missing-field findings we describe in marketplace product content and quality score apply to measurement fields as well.
Size chart image and Size Finder
If the only thing a buyer has to go on is the label, returns are inevitable. Two tools change that. The first is a size chart image: chest, waist, hip and length per size, prepared in the target market's units. Bulutegra's Content Studio generates this image from the measurements on the product record and sends it to the channel together with the multilingual description.
The second is Size Finder: the buyer enters height and weight and the system suggests a size from the product's own list. This runs on your own store; on marketplaces the size chart and the guidance in the description do the same job. Setup details are in cutting returns with Size Finder.
Size fields differ by channel
Every marketplace asks for size in a different place. On Amazon size is a variation theme and you select a country-specific size system; on Etsy the variation name is free text you define; eBay has separate fields such as "US Size" and "EU Size" depending on category; Ozon and Wildberries expect the Russian size sequence. If the conversion rule reads from the product's list, sending the right value to each channel's own field is a matter of one definition. Typing sizes by hand per channel turns into inconsistency by the fourth channel.
Size and unit checklist
- Does every product's master record hold its own size list, in order?
- Are chest, waist, hip and length (apparel) or insole length (footwear) entered per size in centimetres?
- Does the "one size up" rule for the US work from the product's list or from a fixed chart?
- Is each channel's size field and unit expectation defined?
- Was the size chart image generated in the target market's units?
- Does the line item reaching your warehouse show your size or the label the buyer selected?
- Do you track the share of returns with "size" as the reason?
Item six is the critical one: if conversion happens only on the listing and not on the order, the warehouse picks the label the buyer chose, and the exact return you wanted to prevent happens anyway.
How it works with Bulutegra
Bulutegra reads size conversion from the size list on the product record; on US orders it converts one size up and writes the order to the ERP with your size. Content Studio produces the size chart image and multilingual description; Size Finder gives a suggestion from height and weight on your own store. The quality tab lists products with missing size or measurement fields, and you fix them with one click. See the Solutions section for the full module list, and the cross-border marketplace integration guide for the wider international setup.
To see how conversion works with your own size lists, request a demo.
Frequently asked questions
How do I convert Turkish or EU sizes to US sizes?
Generic charts are a starting point, not the final word; the same letter size maps to different measurements at different brands. The reliable method is to define the conversion on each product's own size list. Because US fits run larger, a "one size up" rule works for many Turkish and European manufacturers.
Should Amazon dimensions be in inches or centimetres?
Amazon.com expects inches and pounds; Amazon.de and other European sites expect centimetres and grams. Keep one unit on the product card and convert per channel so the numbers stay consistent.
How can I reduce size-related returns?
A size chart image with real measurements per size, descriptions in the target market's units, and a Size Finder on your own store that suggests a size from height and weight noticeably cut "too tight" and "too loose" returns.
