ISO 6549:2026

• Abstract:

  This document defines a three-dimensional H-point machine for use in the determination of the actual H-point and torso angle of a seat, for the purpose of comparing these measurements to the manufacturer's seating reference point and design torso angle. The three-dimensional H-point machine is intended to be used as a checking device for one designated seat position at a time and is not a device which measures or indicates an occupant's capabilities or comfort. This document is applicable to any motor vehicle where: the distance, vertically measured, between the operator heel point and the seating reference point is less than 550 mm, the torso angle is greater than 5° rearward of vertical or where the attitude of the thigh centreline as indicated by the thigh bar is greater than 5° above the horizontal.

• Status: Published
• Publication Date: 14-Sep-2026
• ICS: 43.020 - Road vehicles in general
• Technical Committee: ISO/TC 22/SC 39 - Ergonomics
• Drafting Committee: ISO/TC 22/SC 39/WG 7 - Hand reach and R and H point determination
• Current Stage: 6060 - International Standard published
• Start Date: 15-Sep-2026
• Due Date: 02-Jul-2027
• Completion Date: 15-Sep-2026

• Revises: ISO 6549:1999 - Road vehicles — Procedure for H- and R-point determination
• Effective Date: 06-Jun-2022

ISO 6549:2026 is an International Standard from ISO for determining the actual H-point and torso angle of a road vehicle seat with a three-dimensional H-point machine. It specifies how to set up the machine, position the seat, and record the measurements so they can be compared with the manufacturer’s seating reference point, also called the R-point or SgRP, and the design torso angle.

What does ISO 6549:2026 specify?

ISO 6549:2026 specifies a checking procedure for one designated seat position at a time, using a three-dimensional H-point machine. It is organized into scope, normative references, terms and definitions, a description of the machine, and the installation procedure, followed by a bibliography.

The scope sets the vehicle applicability conditions: the standard applies where the operator heel point to seating reference point distance is under 550 mm, the torso angle is more than 5° rearward of vertical, or the thigh centreline is more than 5° above horizontal. In practice, this tells a user whether the seat geometry is the kind this procedure was written for.

What are the key requirements of ISO 6549:2026?

ISO 6549:2026 gives a step-by-step method for preparing the vehicle, installing the H-point machine, and reading the results. The main requirement is to place the machine in a repeatable way so the measured actual H-point and actual torso angle can be compared with the manufacturer’s reference values.

Machine description and setup

Clause 4 describes the three-dimensional H-point machine as a reinforced plastic and metal device that represents average adult male torso and seat contours. It uses adjustable thigh and lower leg elements, quadrants for angles, foot and shoe assemblies, spirit levels, and body element weights equivalent to a 76 kg male. In practice, this is the tool that makes the seat comparison repeatable.

Vehicle and seat preparation

Clause 5.1 requires the vehicle and seat to be conditioned at the manufacturer’s discretion at 20 °C ± 10 °C so the seat material reaches room temperature. If the seat has never been sat upon, a 70 kg to 80 kg person or device is used to flex the cushion and back, and the seat may be left unloaded for at least 30 min before installation. This matters because seat foam and trim can change the measurement.

Positioning the vehicle and seat

Clause 5.2 places the vehicle in the three-dimensional reference system using fiducial marks, with the seat set at the seating reference point and all adjustments set as specified by the manufacturer. For seats with independent vertical adjustment or suspension, the vertical position is fixed in the manufacturer’s chosen position. This is the basis for comparing the measured H-point to the design reference.

Installing and loading the H-point machine

Clause 5.3 calls for muslin cotton cloth between the machine and the seat, and suitable floor covering under the feet when needed. Clauses 5.5 to 5.15 cover leg-length selection, foot placement, levelling, forward and rearward loading, and the optional side-to-side rocking step to release friction. A load of 100 N ± 10 N is applied at the hip angle quadrant and T-bar housing area, then the torso is returned to the seat back and the weights are installed. In practice, the procedure tries to remove friction and settling effects before the final reading.

Driver and passenger seat positions

Clauses 5.8 and 5.9 separate driver and passenger procedures. For driver positions, the machine is set up for 50th percentile or 95th percentile leg lengths, with special handling for accelerator pedal contact and a minimum foot angle of 87° for the 95th percentile case. For passenger seats, the feet are generally set 254 mm apart and equidistant from the centreplane, with special instructions for outside front, outside rear, and centre seats. This is the part users follow when they need a seat-specific measurement setup.

Recording the result

Clause 5.16 requires the actual H-point coordinates to be measured in the three-dimensional reference system and, if needed, the actual torso angle to be read from the hip angle quadrant. Clause 5.17 requires a 30 min unloaded period before any rerun. That helps keep repeated measurements comparable.

What terms does ISO 6549:2026 define?

• three-dimensional H-point machine - the device used to determine the actual H-point and actual torso angle in a vehicle.
• H-point - the pivot centre of the machine’s torso and thigh, used as the reference for actual H-point determination.
• seating reference point, R-point, SgRP, design H-point - the manufacturer’s intended H-point location used as the fundamental reference for occupant accommodation.
• actual H-point - the H-point measured with the machine when the seat is positioned at the seating reference point.
• torso angle - the angle, in side view, of the lower flat portion of the torso pan from vertical.
• actual torso angle - the angle between a true vertical line through the actual H-point and the torso line of the installed machine.
• centreplane of the occupant, C/LO - the Y-coordinate of the R-point for the designated seating position.

Who uses ISO 6549:2026?

ISO 6549:2026 is used by vehicle manufacturers, seat and interior engineers, ergonomics specialists, and test laboratories that need to verify seating geometry. It is also relevant to quality and validation teams that compare a production seat or prototype seat against the manufacturer’s reference point and design torso angle. The procedure is especially useful where seat packaging and driving position need to be checked in a consistent way.

What changed in ISO 6549:2026 from the previous edition?

ISO 6549:2026 is the third edition and cancels and replaces ISO 6549:1999. The foreword states that the main changes are editorial.

Which standards are used with ISO 6549:2026?

ISO 3833 is the normative reference and provides the road-vehicle types and definitions used in this standard. The bibliography also cites ISO 4130 for the three-dimensional reference system and fiducial marks used when setting up the vehicle, and ISO 4131:1979 for dimensional codes for passenger cars.

What does the ISO 6549:2026 document contain?

The document contains a machine description, a detailed installation procedure, and two figures. Figure 1 gives the dimensions of the H-point machine elements and the load distribution for the 50th and 95th percentile leg lengths, while Figure 2 identifies the machine parts such as the torso pan, seat pan, thigh bar, hip angle quadrant, and foot angle quadrant. Clause 5 gives the practical sequence for conditioning, setting up, loading, levelling, and measuring the seat position.

International
Standard
ISO 6549
Third edition
Road vehicles — Procedure for H-
2026-09
and R-point determination
Véhicules routiers — Procédure de détermination des points H et
R
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 Description of the three-dimensional H-point machine . 3
5 Installation procedure for the three-dimensional H-point machine . 3
Bibliography . 9

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 22, Road vehicles, Subcommittee SC 39,
Ergonomics.
This third edition cancels and replaces the second edition (ISO 6549:1999), which has been technically
revised.
The main changes are as follows:
— editorial changes.
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 6549:2026(en)
Road vehicles — Procedure for H- and R-point determination
1 Scope
This document defines a three-dimensional H-point machine for use in the determination of the actual
H-point and torso angle of a seat, for the purpose of comparing these measurements to the manufacturer's
seating reference point and design torso angle. The three-dimensional H-point machine is intended to be
used as a checking device for one designated seat position at a time and is not a device which measures or
indicates an occupant's capabilities or comfort.
This document is applicable to any motor vehicle where:
a) the distance, vertically measured, between the operator heel point and the seating reference point is
less than 550 mm,
b) the torso angle is greater than 5° rearward of vertical or where the attitude of the thigh centreline as
indicated by the thigh bar is greater than 5° above the horizontal.
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 3833, Road vehicles — Types — Terms and definitions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 3833 and the following 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/
3.1
three-dimensional H-point machine
device used for the determination of the actual H-point (3.2.2) and actual torso angle (3.3.2) in a vehicle
3.2
H-point
pivot centre of the torso and thigh of the three-dimensional H-point machine (3.1) which simulates the pivot
centre of the human torso and thigh and is used for actual H-point (3.2.2) determination
Note 1 to entry: It is located on the centreplane of the device which is midway between the H-point sight buttons on
either side of the H-point machine.
3.2.1
seating reference point R-point
SgRP
design H-point
manufacturer's intended location for H-point (3.2), which is specifically designated as R-point or SgRP, and
which:
a) is the fundamental reference point used to establish occupant accommodation tools and dimensions;
b) simulates the position of the pivot centre of the human torso and thigh;
c) has coordinates established with respect to the designed vehicle structure;
d) establishes the rearmost normal design driving or riding H-point (3.2) location of each designated
seating position, which accounts for all modes of adjustment: horizontal, vertical and tilt that are
available for the seat, but does not include seat travel used for purposes other than normal driving and
riding
3.2.2
actual H-point
H-point (3.2) measured at the pivot centre of the torso line (3.3.1) and thigh bar centreline of the three-
dimensional H-point machine (3.1) using one of the appropriate leg lengths shown in Figure 1, with the seat
positioned at the seating reference point as specified by the manufacturer
3.3
torso angle
angle from vertical in side view of the lower flat portion of the torso pan of the H-point machine
3.3.1
torso line
centreline of the headroom probe in its fully rearward position against the torso pan of the three-dimensional
H-point machine (3.1)
Note 1 to entry: See Figure 2.
Note 2 to entry: The torso line intersects the H-point (3.2) and is parallel to the flat portion of the torso pan that
defines torso angle (3.3).
3.3.2
actual torso angle
angle measured between a true vertical line through the actual H-point (3.2.2) and the torso line (3.3.1) of
the three-dimensional H-point machine (3.1) installed in accordance with clause 5
Note 1 to entry: Torso angle is read from an indicator, called the hip angle quadrant, located just below the torso angle
(3.3) level on the H-point machine.
3.3.3
design torso angle
angle measured between a true vertical line through the seating reference point and the torso line (3.3.1)
Note 1 to entry: This angle is specified by the manufacturer.
3.4
centreplane of the occupant
C/LO
Y-coordinate of the R-point, in each designated seating position
Note 1 to entry: In vehicles with individual seats, the centreplane of the seat represents the centreplane of the
occupant. On bench seats, the centreplane of the occupant is specified by the manufacturer.
3.5
operator heel point
intersection of the right heel of the three-dimensional H-point machine (3.1) with the surface of the depressed
floor covering or other heel support, when the driver's seat is positioned at the seating reference point

3.6
foot angle
angle measured between the lower leg centreline and a line tangential to the bottom of the bare right foot
Note 1 to entry: A scale on the foot assembly of the three-dimensional H-point machine (3.1) indicates the foot angle. The
angle to the bottom of the device's shoe is 6,5° less than the bare foot angle because of the shoe sole and heel thickness.
4 Description of the three-dimensional H-point machine
The torso and seat pans of the three-dimensional H-point machine (see Figure 2) are representations of
1)
average torso and seat contours of an adult male.
Constructed of reinforced plastic and metal, these separate torso and seat pans simulate the human torso
and thigh and are mechanically hinged at the actual H-point to measure the actual torso angle. An adjustable-
length thigh bar, attached to the seat pan, establishes the thigh centreline and serves as a baseline for the
hip angle quadrant.
Lower leg segments, also adjustable in length, are connected to the seat pan assembly at the T-bar joining
the knees. The T-bar is a lateral extension of the adjustable thigh bar. Quadrants are incorporated in the
lower leg segments to measure knee angles. Shoe and foot assemblies are calibrated to measure the foot
angle. Positive stops are provided in the thigh and lower leg segments for the 50th and 95th percentile of
adult male dimensions (see Figure 1). Two spirit levels orient the device in space. Body element weights are
placed at the corresponding centres of gravity to provide seat penetration equivalent to a 76 kg male. All
2)
joints of the H-point machine shall be checked for free movement without encountering noticeable friction.
5 Installation procedure for the three-dimensional H-point machine
5.1 The vehicle shall be preconditioned at the manufacturer's discretion, at a temperature of (20 ± 10) °C
to ensure that the seat material reaches room temperature. If the seat to be checked has never been sat upon,
a 70 kg to 80 kg person or device shall sit on the seat to flex the cushion and back. At the manufacturer's
request, all seat assemblies shall remain unloaded for a minimum period of 30 min prior to installation of
the three-dimensional H-point machine.
5.2 Dimensions are measured relative to the vehicle three-dimensional reference system by setting up the
vehicle relative to the f
...