Attribute Guide

size_system Attribute in Google Shopping: International Apparel Sizing Guide

Complete guide to the size_system attribute in Google Merchant Center. All allowed values (US, UK, EU, DE, FR, JP, and more), why it is required for…

Updated 3 min readBoostora Team
size_system — Size Ambiguity Without vs. With

Women's Linen Shirt — US Size 8

€64.00us-fashion-brand.com
US 8 = EU 38System: US

Google displays size with context. British shoppers see the equivalent EU/UK size. Correct expectations → fewer returns.

Women's Linen Shirt — Size 8

€64.00us-fashion-brand.com

US women's 8 = UK 12 = EU 38 = JP 11. A British shopper sees "Size 8" and assumes UK sizing (actually a US 4). Orders it. It's two sizes too small. Returns it. Return costs the merchant €12.

A US women's size 8 is a UK size 12, EU size 38, and Japanese size 11. Without size_system, Google cannot normalise your sizes for international shoppers — leading to incorrect size selection, higher returns, and worse seller ratings.

What is the size_system attribute?

The size_system attribute specifies which country’s sizing standard a product uses. Without it, a “Size 8” is ambiguous — it means different things in US, UK, EU, Japanese, and Brazilian sizing systems. Google uses size_system to correctly interpret and normalise your size values when displaying them to shoppers in different markets.

For domestic merchants selling exclusively in their home market, this ambiguity may be negligible. For any merchant whose products are discovered cross-border — which is most merchants on Google Shopping — missing or incorrect size_system is a direct cause of sizing-related returns, which represent 34% of all e-commerce returns industry-wide (Baymard Institute).

Technical specifications

Feed namesize_system
RequiredOptional — strongly recommended for all apparel, especially cross-border
Applies toApparel & Accessories products with a size attribute
Values (exact)US, UK, EU, DE, FR, JP, CN, IT, BR, MEX, AU, KR
Max values per product1 — submit only one per product
CaseUppercase only (e.g., US not us)

Size equivalency table (women’s clothing example)

US024681012
UK46810121416
EU32343638404244
JP57911131517

A US size 8 is a UK 12, EU 40, and JP 13. Without size_system = US, a British shopper seeing “Size 8” assumes UK sizing and orders a product that is two UK sizes too small.

Rules

  • Must use an exact allowed value from the list above — no free-text country names

  • Only one value per product

  • Must align with the actual sizing convention used by the product’s manufacturer

  • If you are reselling products from multiple manufacturers using different systems, each product row must carry its own correct size_system

  • Always pair with the size attribute — size_system without size has no effect

Best practices

  • Source the size system from the manufacturer — do not assume; check the manufacturer’s size chart to confirm which standard they use (US, EU, JP, etc.).

  • Include for all apparel products, even domestic — the cost is zero and protects you when Google surfaces your products to cross-border shoppers.

  • Pair with size_type for complete size context — size_system tells Google which number system to use; size_type tells Google whether it is regular, petite, plus, etc. Both together give full sizing context.

  • Be consistent across all products from the same supplier — inconsistent size_system values for products from the same manufacturer will cause confusing cross-product size comparisons for shoppers browsing your store in Shopping.

Common mistakes

  • Omitting entirely for cross-border feeds — the most impactful and most common mistake

  • Using lowercase values (eu, us) — rejected; must be uppercase

  • Using full country names (“Europe”, “United States”) — not valid values

  • Submitting multiple values per product — only the first is used; the field is not a list

  • Using EU when the manufacturer uses Italian-specific sizing (should be IT)

  • Not updating when you change supplier and the new supplier uses a different system

Frequently asked questions

What are all the allowed values for size_system?
Google accepts the following exact values (case-sensitive, all uppercase): US, UK, EU, DE, FR, JP, CN, IT, BR, MEX, AU, KR. Submit exactly one value per product. Do not use country names ("Germany"), ISO 3166 codes for unsupported markets, or lowercase values — these will be rejected.
What is the difference between EU, DE, FR, and IT size systems?
These are all considered part of the broader European sizing family but have distinct conventions that differ meaningfully for certain product categories. EU is the general Continental European numeric scale (38, 40, 42…). DE, FR, and IT are country-specific variants that can diverge — particularly for shoes (a French shoe 38 ≠ a German shoe 38 in some brands). Use the most specific value that matches your manufacturer's sizing standard. If your sizing comes from an Italian manufacturer using Italian conventions, use IT.
Do I need size_system if I only sell in one country?
For single-market domestic-only feeds, size_system is optional because Google defaults to interpreting sizes using the target country's standard. However, it is still recommended because: (a) Google's auto-detection is not always reliable, (b) shoppers from other countries still discover your products via Shopping, and (c) adding it explicitly protects you if you later expand internationally. The cost of including it is zero; the cost of omitting it when expanding is a flood of incorrectly ordered items.
Should I submit one size_system per product or per feed?
size_system is a product-level attribute — one value per product (per row in your feed). If your catalogue mixes products from manufacturers using different size systems (e.g., some US-branded, some EU-branded), each product should carry the correct size_system for that specific product's sizing standard. You cannot set a single size_system for the whole feed via a feed-level setting.
Does size_system affect Shopping ads performance directly?
size_system does not directly boost impressions or CTR like title or GTIN do. Its impact is on downstream metrics: correct size interpretation reduces return rates, improves seller ratings over time, and prevents product reviews citing "sizing ran completely different to what I expected." For cross-border fashion merchants, return rates from sizing confusion are a significant hidden cost — typically 2–5% of orders in affected markets.
What happens if I submit the wrong size_system?
Google will interpret your size values using the wrong conversion table — a US 8 declared as EU 8 would be converted to a completely different actual size when displayed to shoppers. This causes the same problem as omitting the attribute: shoppers order the wrong size. The error is silent — there is no Diagnostics warning for a plausible but incorrect size_system value. Ensure size_system reflects the actual sizing convention used by the manufacturer of each product.

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