HRB400 and HRB500 are the two dominant grades of hot-rolled deformed rebar for reinforced concrete in China, the Middle East and parts of Asia. This guide compares the two grades on strength, ductility and code compliance, with selection guidance for typical building, bridge and infrastructure projects.
HRB400 and HRB500 are Chinese GB-standard hot-rolled ribbed steel bars for the reinforcement of concrete, named for the minimum yield strength in MPa. HRB400 (minimum yield 400 MPa) is the workhorse grade for typical residential and commercial building construction in China and a growing number of export markets. HRB500 (minimum yield 500 MPa) is the higher-strength grade for high-rise buildings, long-span bridges, and infrastructure projects where reduced rebar tonnage or improved seismic performance matters.
HRB400 vs HRB500: Strength and Ductility
HRB400 has minimum yield strength of 400 MPa and minimum tensile strength of 540 MPa, with minimum elongation at fracture of 16% for bar sizes up to 32 mm. HRB500 has minimum yield of 500 MPa and minimum tensile of 630 MPa, with similar elongation. The 25% higher yield strength of HRB500 allows designers to reduce rebar cross-section for the same design load, typically saving 15–20% of the rebar tonnage in a heavily reinforced member. The trade-off is slightly reduced ductility, which matters for seismic design where very high strength rebar may not meet the elongation requirements of the seismic code.
When HRB400 Is the Right Specification
HRB400 is the right specification for typical residential buildings, low-rise commercial buildings, light industrial structures, and any concrete member where the design is governed by serviceability rather than ultimate strength. HRB400 is also widely used for the secondary reinforcement (stirrups, links, distribution bars) even when the main bars are HRB500, since the cost saving is significant and the strength is more than sufficient. For seismic design in moderate zones, HRB400 typically meets the elongation requirement without issue.
When HRB500 Is the Necessary Upgrade
HRB500 is the right specification for high-rise building columns and beams, long-span bridge girders, large foundation mats, and any heavily loaded concrete member where reducing the rebar congestion is critical. The higher strength allows smaller diameter bars to be used for the same design force, which makes the rebar cage easier to place and concrete easier to pour. HRB500 is also increasingly the preferred grade for seismic design in high-intensity zones, provided the specific bar meets the elongation and the strength ratio (fy/fu) requirements of the local seismic code.
Bar Sizes, Standards and Seismic Grade
Both HRB400 and HRB500 are produced in nominal diameters from 6 mm to 50 mm, with the most common construction sizes being 8, 10, 12, 16, 20, 25 and 32 mm. The standard is GB 1499.2 for hot-rolled ribbed bars. For seismic applications, the "E" suffix designation (HRB400E, HRB500E) is required, indicating that the bar meets the additional elongation and the strength ratio requirements for seismic design. The "E" grade is a small additional cost and should be specified for any project in a seismic zone.
What to Specify on the Rebar RFQ
State the standard (GB 1499.2), the grade (HRB400 or HRB500, with or without the E suffix for seismic), the nominal diameter, the bar length (typically 9 m or 12 m straight bars, or coils for smaller diameters), the bundle weight, and any supplementary requirements (Charpy impact at low temperature for bridges, epoxy coating for marine exposure). For most building construction, default to HRB400E; for high-rise and heavy infrastructure, default to HRB500E. Always confirm the mill supplies the test report per EN 10204 3.1 with the actual yield, tensile and elongation values.
Related Resources from Baobin Steel
- Steel bar catalog – rebar, round bar and angle
- Structural steel overview – grades and standards
- Request a quote – send your rebar schedule for pricing