ISO 1035:2026

Hot-rolled steel bars — Dimensions, shape, masses and tolerances

This document specifies dimensions, shape, mass and tolerances of metric series hot-rolled steel bars. This document is applicable to: hot-rolled round bars with diameter of 5,5 mm up to 400 mm; hot-rolled square bars with side length of 5,5 mm up to 300 mm; hot-rolled flat bars with thickness of 3 mm up to 60 mm and width of 10 mm up to 200 mm; hot-rolled hexagonal bars with distance across opposite flats of 8 mm up to 70 mm; hot-rolled octagonal bars with distance across opposite flats of 16 mm up to 40 mm. NOTE Wide flats can be covered under flat bars for practical reasons.

Barres en acier laminées à chaud — Dimensions, formes, masses et tolérances

General Information

• Status: Published
• Publication Date: 10-May-2026
• ICS: 77.140.60 - Steel bars and rods
• Technical Committee: ISO/TC 17/SC 3 - Steels for structural purposes
• Current Stage: 6060 - International Standard published
• Start Date: 11-May-2026
• Due Date: 29-May-2027
• Completion Date: 11-May-2026

Relations

• Revises: ISO 1035-4:1982 - Hot-rolled steel bars — Part 4: Tolerances
• Effective Date: 01-Jun-2024
• Revises: ISO 1035-3:1980 - Hot-rolled steel bars — Part 3: Dimensions of flat bars
• Effective Date: 01-Jun-2024
• Revises: ISO 1035-2:1980 - Hot-rolled steel bars — Part 2: Dimensions of square bars
• Effective Date: 01-Jun-2024
• Revises: ISO 1035-1:1980 - Hot-rolled steel bars — Part 1: Dimensions of round bars
• Effective Date: 01-Jun-2024

Overview

ISO 1035:2026 provides a comprehensive international standard for the dimensions, shape, mass, and tolerances of hot-rolled steel bars in metric series. Developed by ISO Technical Committee ISO/TC 17, Steels, this standard covers various cross-sectional shapes of steel bars including round, square, flat, hexagonal, and octagonal forms. ISO 1035:2026 is designed to harmonize the specification of hot-rolled steel bars across industries, supporting consistency in quality and manufacturing processes worldwide. This document supersedes previous editions (ISO 1035-1:1980 through ISO 1035-4:1982) with revised and expanded requirements.

Key Topics

• Scope of Application:
  • Covers hot-rolled round bars (5.5 mm to 400 mm diameter), square bars (5.5 mm to 300 mm side), flat bars (3 mm to 60 mm thickness, 10 mm to 200 mm width), hexagonal bars (8 mm to 70 mm across flats), and octagonal bars (16 mm to 40 mm across flats).
  • Metric series ensures widespread compatibility for international use.
• Dimensional Specifications:
  • Detailed preferred dimensions, masses per unit length, and sectional areas for each type of bar.
  • Tolerance classes (normal, fine, superfine for rounds and squares; class N, F for hexagons and octagons) ensure precision based on application needs.
• Shape & Form Control:
  • Permissible levels of ovality and out-of-squareness for each bar shape help maintain cross-sectional integrity.
  • Requirements for straightness and, when specified, twist are described, enhancing structural reliability.
• Contractual Flexibility:
  • Provisions for supplier and purchaser agreements on non-standard dimensions, tolerances, and special requirements such as sharp corners or radius.
• Measurement and Tolerances:
  • Systematic tables address tolerances on length, width, thickness, and straightness.
  • Recommendations for distance from bar ends for tolerance measurements ensure uniformity in product acceptance.

Applications

• Structural Engineering: Used as fundamental building elements for construction, bridges, frameworks, and reinforcement.
• Automotive and Machinery: Essential in manufacturing components that require consistent shape and mass, supporting mechanical performance.
• General Manufacturing: Suitable for fabrication of parts in various industries where standardized steel bar dimensions are critical for production efficiency and interchangeability.
• Procurement and Quality Assurance: Provides a clear reference for ordering, inspection, and acceptance of hot-rolled steel bars on a global scale.

By adopting ISO 1035:2026, organizations ensure that hot-rolled steel bars meet international best practices for dimensional accuracy, physical consistency, and mass properties - supporting reliable design, manufacturing, and structural safety.

Related Standards

For compatibility and further technical information, ISO 1035:2026 references and relates to several international and regional standards:

• ISO 6929: Steel Products – Vocabulary
• EN 10058, EN 10059, EN 10060, EN 10061: European standards for hot-rolled flat, square, round, and hexagonal steel bars
• GB/T 702: Hot-rolled steel bars – Dimensions, shape, mass, and tolerances (China)
• ASTM A6M: General requirements for rolled structural steel bars (USA)
• ISO 630 Series: Structural steels and technical delivery conditions
• ISO 7452: Tolerances on dimensions and shape for hot-rolled steel plates
• JIS G 3191, JIS G 3194: Japanese standards for hot-rolled steel bars

These references ensure alignment with global steel industry requirements and facilitate smooth international trade in steel products.

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Keywords: hot-rolled steel bars, ISO 1035, steel bar dimensions, shape and tolerances, metric series steel bars, standard steel bar masses, structural steel standards, steel product specifications

Standards Content (Sample)

International
Standard
ISO 1035
First edition
Hot-rolled steel bars — Dimensions,
2026-05
shape, masses and tolerances
Barres en acier laminées à chaud — Dimensions, formes, masses
et tolérances
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Designation . 1
5 Cross-sectional form . 2
6 Dimensions, masses and tolerances . . 3
6.1 Dimensions and masses.3
6.2 Tolerances on dimensions .4
7 Shape . 5
Annex A (informative) Dimensions, sectional areas and masses per unit length of hot-rolled
steel bars .10
Bibliography . 19

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 17, Steels, Subcommittee SC 3, Steels for
structural purposes.
This first edition of ISO 1035 cancels and replaces ISO 1035-1:1980, ISO 1035-2:1980, ISO 1035-3:1980 and
ISO 1035-4:1982, which have been technically revised.
The main changes are as follows:
— figures illustrating forms of hot-rolled bars have been added;
— the category of dimensions and second preference dimensions has been cancelled;
— upper limits of dimensions and dimensional tolerances for hot-rolled round, square and flat bars have
been revised;
— dimensions for hexagonal and octagonal bars have been added;
— requirement for maximum permissible value for hot-rolled flat bars was added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
International Standard ISO 1035:2026(en)
Hot-rolled steel bars — Dimensions, shape, masses and
tolerances
1 Scope
This document specifies dimensions, shape, mass and tolerances of metric series hot-rolled steel bars.
This document is applicable to:
a) hot-rolled round bars with diameter of 5,5 mm up to 400 mm;
b) hot-rolled square bars with side length of 5,5 mm up to 300 mm;
c) hot-rolled flat bars with thickness of 3 mm up to 60 mm and width of 10 mm up to 200 mm;
d) hot-rolled hexagonal bars with distance across opposite flats of 8 mm up to 70 mm;
e) hot-rolled octagonal bars with distance across opposite flats of 16 mm up to 40 mm.
NOTE Wide flats can be covered under flat bars for practical reasons.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 6929, Steel products — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 6929 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Designation
The designation of hot-rolled steel bars shall comprise:
— the term round bar, square bar, flat bar, hexagonal or octagonal bar;
— the number of the standard, i.e. ISO 1035;
— the nominal dimension(s) in mm and the tolerance classes;
— the number of the quality standard and the steel name of the ordered steel.
EXAMPLE
Round bar ISO 1035-50 N×6000L0

Steel ISO 630-2 S355D
5 Cross-sectional form
5.1 Cross-sectional forms of hot-rolled round bars and square bars are shown in Figure 1.
a) b)
Key
d diameter
a side length
Figure 1 — Cross-sectional forms of hot-rolled round bars and square bars
5.2 Cross-sectional form of hot-rolled flat bars is shown in Figure 2.
Key
w width
t thickness
Figure 2 — Cross-sectional form of hot-rolled flat bars
5.3 Cross-sectional forms of hot-rolled hexagonal and octagonal bars are shown in Figure 3.

a) b)
Key
S distance across flats
Figure 3 — Cross-sectional forms of hot-rolled hexagonal and octagonal bars
6 Dimensions, masses and tolerances
6.1 Dimensions and masses
6.1.1 The preferred dimensions and masses per unit length of hot-rolled round bars are given in Table A.1.
6.1.2 The preferred dimensions and masses per unit length of hot-rolled square bars are given in Table A.2.
6.1.3 The preferred dimensions and masses per unit length of hot-rolled flat bars are given in Table A.3.
6.1.4 The preferred dimensions, sectional areas and masses per unit length of hot-rolled hexagonal and
octagonal bars are given in Table A.4.
6.1.5 Upon agreement between the supplier and purchaser, steel bars may be delivered in other dimensions
unlisted in Annex A, and it shall be indicated in the contract.

6.2 Tolerances on dimensions
6.2.1 The tolerances on diameter for round bars and side length for square bars shall be as specified
in Table 1. The class of dimensional tolerance shall be indicated in the contract. If no tolerance class is
requested, the tolerance class is N.
Table 1 — Tolerances on diameter for round bars and side length for square bars
Tolerance on diameters or side lengths for classes
Nominal diameters or side lengths
mm
mm
N F S
5,5-15 ±0,40 ±0,30 ±0,20
>15-25 ±0,50 ±0,40 ±0,25
>25-35 ±0,60 ±0,50 ±0,30
>35-50 ±0,80 ±0,60 ±0,40
>50-80 ±1,00 ±0,80 ±0,50
>80-100 ±1,30 ±1,00 ±0,90
>100-120 ±1,60 ±1,30 ±1,20
>120-160 ±2,00 ±1,60 ±1,40
>160-200 ±2,50 ±2,00 ±1,60
>200-280 ±3,00 ±2,50 ±2,00
>280-310 ±4,00 ±3,00 ±2,50
>310-380 ±5,00 ±4,00 ±3,00
>380-400 ±6,00 ±5,00 ±4,00
Note: N=normal, F=fine, S=superfine.
6.2.2 The tolerances on width and thickness of hot-rolled steel flat bars shall be as specified in Table 2 and
Table 3.
6.2.3 Tolerances of thickness and width shall not apply for the part of out-of-squareness.
Table 2 — Tolerances on width for hot-rolled flat bars
Nominal widths Tolerances on width
mm mm
10-50 ±0,80
>50-75 ±1,20
>75-100 ±1,50
>100-125 ±2,00
>125-150 ±2,50
>150-200 To be agreed between the supplier and purchaser
Table 3 — Tolerances on thickness for hot-rolled flat bars
Tolerances on thicknesses for nominal widths (w)
Nominal thicknesses
mm
mm
w≤50 50 3-20 ±0,40 ±0,50
To be agreed between the supplier and
>20-40 ±0,80 ±1,00
purchaser
>40-60 — ±1,50
6.2.4 The distance across flats and tolerances of hot-rolled hexagonal and octagonal bars shall be in
accordance with Table 4. The class of tolerances shall be indicated in the contract.
Table 4 — Distance across flats and tolerances for hot-rolled hexagonal and octagonal bars
Tolerance for classes
Distance across flats
mm
mm
N F
8-15 ±0,40 ±0,30
>15-25 ±0,50 ±0,40
>25-35 ±0,60 ±0,50
>35-50 ±0,80 ±0,60
>50-70 ±1,00 ±0,80
6.2.5 The tolerances on length shall be as specified in Table 5. If no tolerance class is requested, the
tolerance class is L1.
Table 5 — Tolerances on length
Tolerances on length for class
mm
Nominal lengths
L0 L1 L2 L3 L4
0 0 0
a c
All ±200
b b b
+100 +50 +25
a
The length of the bar is left to the choice of the manufacturer, it shall be not less than 3 000 mm. If agreed between the
purchaser and the manufacturer, other dimensions and tolerances may be used.
b
When agreed at the time of ordering, the bars can be supplied with symmetrical “±” tolerances. In this case, the total
tolerance range shall be the same as specified for the relevant “+” tolerances (for example ±25 mm instead of 0 +50 mm. Possible
short-length may appear, their percentage and minimum length has to be agreed on during the order.
c
Tighter tolerances in cases where cold cutting is possible might be agreed at the time of enquiry and order.
6.2.6 Upon agreement between the supplier and purchaser, other dimensional tolerances of steel bars
may be used and it shall be indicated in the contract.
7 Shape
7.1 The permissible ovality for all diameters of round bars, measured as the difference between the
maximum and minimum diameters of the same cross-section, shall not exceed 75 % of the total tolerance
specified on the diameter according to Table 1. If agreed between the purchaser and the manufacturer, other
ovality may be used.
7.2 The permissible out-of-squareness for all side lengths of square bars, measured as the difference of
the distance between parallel faces of the same cross-section, shall not exceed 75 % of the total tolerance
specified on the nominal width of side in Table 1. If agreed between the purchaser and the manufacturer,
other out-of-square may be used. The out-of-squareness of square bars are shown in Figure 4 a), b), c) and d).

a) b)
c) d)
Figure 4 — Out-of-squareness of hot-rolled square bars
7.3 The permissible out-of-section for all distances across flats of hexagonal and octagonal bars,
measured as the maximum difference in the distance across opposite flats of the
...