ISO 31-1:1978
(Main)Quantities and units of space and time
Quantities and units of space and time
Grandeurs et unités d'espace et de temps
General Information
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Standards Content (Sample)
INTERNATIONAL STANDARD 31/1
INTERNATIONAL ORGANIZATION FOR STANDARDlZATlON*MEW(L1YHAPOLIHAR OPrAHH3AUWR no CTAHAAPTM3AUMHWRGANlSATlON INTERNATIONALE DE NORMALISATION
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Quantities and units of space and time
Grandeurs et unités d’espace et de temps
First edition - 1978-03-15
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w UDC 53.081 Ref. No. IS0 31/1-1978 (E)
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Descriptors : quantities, units of measurement, time, length, area, volume, definitions, symbols, international system of units.
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FOREWORD
IS0 (the International Organization for Standardization) is a worldwide federation
of national standards institutes (IS0 member bodies). The work of developing
International Standards is carried out through IS0 technical committees. Every
a subject for which a technical committee has been set
member body interested in
up 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.
Draft International Standards adopted by the technical committees are circulated
to the member bodies for approval before their acceptance as International
Standards bv the IS0 Council.
International Standard IS0 31/1 was developed by Technical Committee
ISO/TC 12, Quantities, units, symbols, conversion factors and conversion tables,
and was circulated to the member bodies in July 1975.
It has been approved by the member bodies of the following countries :
Australia Germany Romania
Austria Hungary South Africa, Rep. of
Belgium India Switzerland
Bulgaria Ireland
Thailand
Canada Mexico Turkey
Czechoslovakia Netherlands United Kingdom
Denmark New Zealand U.S.S.R.
France Norway Yugoslavia
The member bodies of the following countries expressed disapproval of the
document on technical grounds :
Japan*
Sweden
U.S.A.**
*
Disagreement concerning the decimal marker only.
**
Remark on supplementary units only.
This International Standard cancels and replaces IS0 Recommendation
R 31/1-1965, on which it constitutes a technical revision.
O International Organization for Standardization, 1978 0
Printed in Switzerland
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IS0 31/1-1978 (E)
I NTE RNATl ON AL STANDARD
Quantities and units of space and time
All units between two full lines belong to the quantities
INTRODUCTION
between the corresponding full lines on the left-hand pages.
This document, containing a table of quantities and units
Where the numbering of the items has been changed in the
of space and time, is part I of IS0 31, which deals with
revision of a part of IS0 31, the number in the preceding
quantities and units in the various fields of science and
is shown in parentheses on the left-hand page under
edition
technology. The complete list of parts of IS0 31 is as
the new number for the quantity; a dash is used to indicate
- follows :
that the item in question did not appear in the preceding
Part O : General introduction - General principles
edition.
concerning quantities, units and symbols.
Part I : Quantities and units of space and time.
Tables of quantities
Part II : Quantities and units of periodic and related
The most important quantities within the field of this
phenomena.
document are given together with their symbols and, in
most cases, definitions. These definitions are given merely
Part I I I : Quantities and units of mechanics
for identification; they are not intended to be complete.
Part IV : Quantities and units of heat
The vectorial character of some quantities is pointed out,
Part V : Quantities and units of electricity and
especially when this is needed for the definitions, but no
magnetism.
attempt is made to be complete or consistent.
Part VI : Quantities and units of light and related
In most cases only one symbol for the quantity is given’ );
electromagnetic radiations
where two or more symbols are given for one quantity
and no special distinction is made, they are on an equal
Part VI I : Quantities and units of acoustics.
footing.
Part VI I I : Quantities and units of physical chemistry
and molecular physics
Tables of units
-
Part IX : Quantities and units of atomic and nuclear
Units for the corresponding quantities are given together
physics.
with the international symbols and the definitions. For
further information, see also part O.
Part X : Quantities and units of nuclear reactions and
ionizing radiations.
The units are arranged in the following way :
Part XI : Mathematical signs and symbols for use in the
1) The names of the SI units are given in large print
physical sciences and technology.
(larger than text size). The SI units and their decimal
by means of the SI
multiples and sub-multiples formed
Part XI I : Dimensionless parameters.
prefixes are particularly recommended. The decimal
Part XI I I : Quantities and units of solid state physics
multiples and sub-multiples are not explicitly
mentioned.
Arrangement of the tables
2) The names of non-SI units which may be used
The tables of quantities and units in IS0 31 are arranged together with SI units because of their practical
importance or because of their use in specialized fields
so that the quantities are presented on left-hand pages and
are given in normal print (text size).
the units on corresponding right-hand pages.
1) When two types of sloping letters exist (for example as with 9, O; 9, 9; g, g) only one of these is given. This does not mean that the other
is not equally acceptable.
1
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IS0 31/1-1978 (E)
3) The names of non-SI units which may be used
ratios of two lengths and of two areas respectively, and
temporarily together with SI units are given in small consequently they are treated as dimensionless quantities.
print (smaller than text size). Although in this treatment the coherent unit for both
quantities is the number 1, it is convenient to use the
The units in classes 2 and 3 are separated by a broken
1
special names radian and steradian instead of the number
line from the SI units for the quantities concerned.
in many practical cases.
4) Non-SI units which should not be used together
If plane angle and solid angle were treated as base
with SI units are given in annexes in some parts of
quantities, the units radian and steradian would be base
IS0 31. The annexes are not integral parts of the
units and could not be considered as special names for
standard. They are arranged in three groups :
the number 1. Such a treatment would require extensive
changes in IS0 31.
a) Units of the CGS-system with special names
Number of digits in numerical statements' )
It is generally preferable not to use CGS-units with
special names and symbols together with SI units.
All numbers in the column "Definition" are exact.
b) Units based on the foot, pound and second and
In the column "Conversion factors" the conversion factors
some other units
on which the calculation of others are based are normally
given to seven significant digits. When they are exact and
c) Other units
contain seven or fewer digits and where it is not obvious
These are given for information, especially regarding
from the context, the word !'exactly" is added, but when
the conversion factor. The use of those units marked
they can be terminated after more than seven digits they
f is deprecated.
with
may be given in full. When the conversion factors are
derived from experiment, they are given with the number
of significant digits justified by the accuracy of the
Remark on supplementary units experiments. Generally, this means that in such cases the
last digit only is in doubt. When, however, experiment
The Conférence générale des poids et mesures (CGPM :
justifies more than seven digits, the factor is usually
General Conference for Weights and Measures) has classified
rounded off to seven significant digits.
the SI units, radian and steradian, as "supplementary
units", deliberately leaving open the question of whether The other conversion factors are given to not more than six
they are base units or derived units, and consequently the significant digits; when they are exactly known and contain
question of whether angle and solid angle are to be six or fewer digits and where it is not obvious from the
considered as base quantities or derived quantities. context, the word "exactly" is added.
a precision
In IS0 31, plane angle and solid angle are treated as derived Numbers in the column "Remarks" are given to
appropriate to the particular case.
quantities (see also part O). They are defined in IS0 31 as
1) The decimal sign is a comma on the line. In documents in the English language, a comma or a dot on the line may be used.
2
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IS0 31/1-1978 (E)
1. Space and Time
Quantities
1-1.1 . . . 1-3.7
~~
Item
Definition Remarks
Quantity Symbol
No.
The angle between two half-lines According to this definition,
1-1.1 angle
terminating at the same point is angle is a dimensionless quan-
(plane angle)
tity; however, also see the
defined as the ratio of the arc
introduction
cut out on a circle (with its
centre at that point) to the
radius of the circle
According to this definition,
The solid angle of a cone is
1-2.1 solid angle
solid angle is a dimensionless
defined as the ratio of the area
quantity; however, also see the
cut out on a spherical surface
introduction
(with its centre at the apex of
that cone) to the square of the
radius of the sphere
1-3.1 length
1-3.2 breadth
1-3.3 height
1-3.4 thickness
1-3.5 radius
1-3.6 d iameter
1-3.7 length of path
L
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IS0 31/1-1978 (E)
1. Space and Time
Units
I-1.a. . 1-3.
-
Name of unit
nternationr
and
Item
Conversion factors Remarks
symbol Definition
in certain cases
No.
for unit
abbreviation
for this name
-
See the introduction
1 rad is the angle
radian
1-1.a
between two radii of a
circle which cut off on
the circumference an
arc equal in length to
the radius
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OTT
1 =-
The degree sho
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