AISI 304 Stainless Steel: UNS S30400 and EN 1.4301 Cross-Reference

Written by: Emma, Technical Sales Engineer  |  Reviewed by: Ethan, Materials Engineer  |  Updated: August 2026

International buyers of stainless steel regularly meet the same grade under several names: AISI 304, UNS S30400, EN 1.4301, and X5CrNi18-10. These designations usually point to the same widely used austenitic stainless steel, but they come from different naming systems — and “equivalent” does not mean “automatically interchangeable.” This article explains what each designation means, how they relate, and how to write a specification that holds up across ASTM and EN standards.

1. What Is AISI 304 Stainless Steel?

AISI 304 is the classic 18-8 austenitic stainless steel, containing roughly 18% chromium and 8% nickel. It offers a well-balanced combination of corrosion resistance, formability, and weldability, which is why it is one of the most specified stainless grades worldwide. In this article, the grade itself is not the main subject; the focus is on how its various designations relate to one another for purchasing and specification purposes.

Because 304 is so common, it appears in multiple national and international systems, and those systems are not identical. Understanding the relationship between them — and where they differ — is what prevents costly specification errors in international trade.

2. 304, UNS S30400 and EN 1.4301: What Each Designation Means

The four names commonly used for this grade belong to different systems, each with a specific meaning:

AISI 304 is the everyday grade name from the American Iron and Steel Institute system. UNS S30400 is the unified numbering designation that places the grade in the S30000 austenitic stainless series. EN 1.4301 is the European material (Werkstoff) number, and X5CrNi18-10 is the corresponding EN steel name, where the “X5” indicates a maximum carbon of roughly 0.05% in the symbolic system and the remainder summarizes the chromium and nickel content. These are labels for the same material concept, not proof that every requirement is identical.

Other national systems add still more names — for example, JIS SUS 304 in Japan and 06Cr19Ni10 in the Chinese GB system. All of these point to the same material concept, which is exactly why international orders benefit from stating the designation system explicitly rather than relying on a single familiar name.

3. Cross-Reference Table: AISI / UNS / EN

The common cross-reference is summarized below. It shows the typical correspondences used in procurement, but it is a guide rather than a guarantee of full equivalence.

4. Chemical Composition: Where the Specifications Overlap and Differ

The grades are closely corresponding, but the exact composition limits are defined separately by each standard system. The table below compares typical limits for UNS S30400 under ASTM A240 and for 1.4301 under the EN 10088 series; the values are illustrative and should be confirmed against the governing specification and product form.

The overlaps are large, but the differences — such as the slightly lower chromium range and the stricter sulfur limit in the EN system — illustrate why the two designations should be cross-referenced, not assumed to be one and the same. A material certified to one standard may not automatically satisfy every limit of the other.

5. EN 1.4301 vs UNS S30400: Equivalent Does Not Mean Automatically Interchangeable

“Equivalent” and “cross-referenced” are useful shorthand, but they are not the same as “identical” or “automatically interchangeable.” The two designations refer to grades with very similar chemistry and general properties, yet each is governed by its own standard with its own composition limits, tolerances, and certification rules.

For routine, non-critical applications, a material certified to one standard is often acceptable in place of the other. For pressure equipment, regulated projects, or safety-critical components, however, substitution must be confirmed against the contract, the product standard, the dimensions and tolerances, the delivery condition, and the required certification. The grade name is only the starting point; the governing specification is what actually binds the order.

This is why formal cross-referencing is best handled at the specification level, not the grade-name level. When an EN-standard component must be supplied with ASTM-certified material — or the reverse — the purchaser should confirm that the material satisfies the specific chemical, mechanical, and certification requirements of the governing standard, rather than assuming the grade name alone carries the compliance over.

6. Product Standards: ASTM A240, A276 and EN 10088

A grade designation is not the same thing as a product standard. “304” tells you what the material is; the product standard tells you what form it is supplied in and what requirements apply to that form. Confusing the two is a common source of specification errors.

In the ASTM system, 304 sheet, plate, and strip are typically ordered to ASTM A240, while 304 bars and shapes are ordered to ASTM A276. In the EN system, the EN 10088 series plays the equivalent role, with separate parts for flat products, long products, and other forms. A 304 order is therefore incomplete until it names both the grade (304, S30400, or 1.4301) and the applicable product standard for the specific form.

7. Product Forms, Dimensions and Certification

Beyond the grade and product standard, a complete order specifies the product form (sheet, plate, bar, and so on), the dimensions and tolerances, the surface finish, and the delivery condition. Certification is the final link: a mill test certificate — commonly to EN 10204 3.1 or 3.2 where applicable — documents that the material actually meets the stated grade and standard.

Because composition and property requirements can vary between ASTM and EN specifications, the certification should match the standard named in the order. A certificate issued against an EN specification is not automatically evidence of compliance with an ASTM specification, even when the grades are commonly cross-referenced.

Dimensional and tolerance conventions can also differ between systems. A thickness, width, or flatness tolerance that is standard under one specification may not match the tolerance class under another, so buyers should confirm tolerances and surface finish alongside the grade rather than assuming they transfer with the designation.

8. 304 vs 304L: Why Buyers Should Not Confuse 1.4301 with 1.4307

A frequent cross-reference error is to treat 1.4301 as if it were the low-carbon 304L. It is not. EN 1.4301 (X5CrNi18-10) corresponds to standard 304, while EN 1.4307 (X2CrNi18-9) corresponds to 304L, with a lower maximum carbon content.

The distinction matters most for welding. The lower carbon of 304L (UNS S30403) reduces the risk of chromium carbide precipitation and intergranular corrosion adjacent to welds, which is why 304L is frequently specified for welded fabrication. Mixing up 1.4301 and 1.4307 can therefore change the welding behavior of the order — a mistake that is easy to avoid by writing the full designation and carbon requirement.

9. Common Cross-Reference and Purchasing Mistakes

• Treating “equivalent” as “identical” — cross-referenced grades are governed by separate standards with separate limits.
• Confusing the grade designation with the product standard — “304” must be paired with ASTM A240, A276, EN 10088, or another applicable standard.
• Writing only “304 stainless steel” — the designation alone leaves form, dimensions, condition, and certification undefined.
• Confusing 1.4301 with 1.4307 (304L) — the carbon difference affects welding behavior.
• Assuming one certificate satisfies another standard — certification must match the specification named in the order.
• Mixing property data across product forms — plate, bar, pipe, and tube have different standards and requirements.

10. How to Specify 304 Across International Standards

A clear international order names the grade, the designation system, the product standard, and the physical and documentary requirements. A practical example might read:

Where both ASTM and EN designations are referenced, the order should also state which standard governs compliance, so there is no ambiguity about which limits and tolerances apply. This is especially important for regulated or safety-critical work.

FAQ

Q1: What is AISI 304 stainless steel?
AISI 304 is the classic 18-8 austenitic stainless steel, widely used for its balanced corrosion resistance, formability, and weldability. Its UNS designation is S30400.

Q2: What is the EN equivalent of AISI 304?
The common European cross-reference is EN 1.4301, with the steel name X5CrNi18-10.

Q3: Is EN 1.4301 the same as 304L?
No. 1.4301 corresponds to standard 304, while 1.4307 (X2CrNi18-9) corresponds to the low-carbon 304L.

Q4: Is UNS S30400 identical to EN 1.4301?
They are closely corresponding grades, but their composition limits and product requirements are defined by separate standards, so they are not automatically interchangeable.

Q5: What is the difference between a grade designation and a product standard?
The grade (304, S30400, 1.4301) identifies the material; the product standard (such as ASTM A240, A276, or EN 10088) defines the form, requirements, and tolerances that apply.

Q6: What does X5CrNi18-10 mean?
It is the EN steel name for 1.4301, summarizing the carbon level (X5) and the approximate chromium (18%) and nickel (10%) content.

Q7: How should I specify 304 for an international order?
State the grade and designation (304 / S30400 / 1.4301), the governing product standard, product form, dimensions, finish, condition, certification, and quantity.