size_system
The regional sizing standard used in the size field. Disambiguates between e.g. UK 12, US 12, and EU 12 — three different physical sizes despite the same number.
Also known as: sizing_region
Channel support
| Channel | Status | Field name | Notes |
|---|---|---|---|
| Google Merchant Center | Recommended | size_system | — Docs → |
| Meta Commerce Manager | Optional | size_system | — |
| TikTok Shop | Optional | size_system | — |
| Pinterest Catalog | Optional | size_system | — |
| Amazon | Optional | size_system | — |
| Bing Merchant Center | Recommended | size_system | — |
Why it matters
Without size_system, channels guess based on locale. A UK-targeted catalogue with US sizing would mismatch users to wrong sizes, increasing returns and hurting conversion. Set it explicitly.
Size_system exists to disambiguate the international sizing chaos. A "size 12" dress could mean UK 12 (medium, EU 40), US 12 (large, EU 42), or JP 12 (closer to a UK 8). Without size_system, channels guess based on locale, and the guesses are wrong often enough to drive significant return rates in cross-border catalogs.
The pattern that works for multi-region sellers: declare size_system explicitly on every apparel item, even when the targeted region matches the sizing system. UK-targeted catalog with UK 12 dresses still benefits from size_system: UK because the explicit declaration prevents channel locale-detection from misinterpreting the size. The minor overhead of including the field universally is worth the certainty.
For US-only or UK-only sellers, size_system is optional but recommended for the same defensive-data-quality reason. The cost of populating is rounding error; the benefit of preventing locale-guess errors is real.
Format rules
-
Two-letter region code (UK, US, EU, etc.)
Applies to: Google Merchant Center, Meta Commerce Manager, Pinterest Catalog, Bing Merchant Center
Valid examples
UK UK sizing
EU European sizing
Common mistakes
British Use 'UK' not the country name
Related fields
FAQ
What if my products use a custom sizing system?
Pick the closest standard region. If the size is genuinely custom (designer-specific, etc.), include the sizing context in the title or description and pick whichever region your target audience uses.
Last reviewed: 26 May 2026
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