IEC 80000-13:2025

Quantities and units - Part 13: Information science and technology

This document specifies names, symbols and definitions for quantities and units used in information science and technology. Where appropriate, conversion factors are also given. Prefixes for binary multiples are also given.

Grandeurs et unités — Partie 13: Science et technologies de l'information

Le présent document spécifie les noms, les symboles et les définitions des grandeurs et unités utilisées dans la science et les technologies de l'information. Des facteurs de conversion sont également indiqués, s'il y a lieu. Des préfixes pour multiples binaires sont aussi donnés.

General Information

• Status: Published
• Publication Date: 19-Feb-2025
• ICS: 01.060 - Quantities and units
• Technical Committee: ISO/TC 12 - Quantities and units
• Drafting Committee: ISO/TC 12 - Quantities and units
• Current Stage: 6060 - International Standard published
• Start Date: 20-Feb-2025
• Due Date: 17-Aug-2025
• Completion Date: 20-Feb-2025

Relations

• Revises: IEC 80000-13:2008 - Quantities and units - Part 13: Information science and technology
• Effective Date: 19-Aug-2023

Overview

IEC 80000-13:2025 - Quantities and units - Part 13: Information science and technology is an international standard (prepared jointly by IEC TC 25 and ISO TC 12) that specifies names, symbols and definitions for quantities and units used in information science and technology. The document also provides conversion information where appropriate and prefixes for binary multiples. This edition replaces the 2008 version and includes technical revisions, notably the addition of new binary prefixes.

Key topics and requirements

• Definition of quantities and symbols: Standardized names and symbols for information‑technology quantities such as traffic intensity (erlang), storage capacity (bit, octet/byte), transfer rate (bit/s, octet/s), periods (T), and modulation/line digit rate (baud).
• Units and coherent SI treatment: Emphasizes use of coherent SI units where applicable, and clarifies when non‑SI or domain‑specific units (e.g., erlang, baud, bit, octet) are accepted for use with the SI.
• Storage and data units: Guidance on expressing storage capacity and equivalent binary storage capacity; recommended use of explicit symbols (bit, o, B) and careful use of the term “byte” for 8‑bit bytes.
• Transfer and timing quantities: Standardizes transfer rates (bits per second, octets per second), periods of data elements, binary digit rate (bit rate) and equivalent binary digit rate.
• Binary prefixes: Incorporates prefixes for binary multiples to reduce ambiguity in expressing binary storage and transfer magnitudes.
• Notation and conventions: Rules on symbol variants, use of the unit one (1) for dimensionless quantities, and exact/approximate notation (=, ≈, :=).

Applications

IEC 80000-13 is essential where consistent measurement, reporting and interoperability of information quantities are required:

• Telecommunications and network engineering (call/traffic models, bit rates, baud rates).
• IT and storage product specification (disk, memory, file‑system capacities, expressing octets/bytes).
• Test labs, metrology and compliance testing that report performance in standardized units.
• Standards writers, technical authors and regulatory bodies that reference quantities and units in specifications and legislation.
• Software developers and system architects producing metrics, logs and performance counters.

Who should use this standard

• Telecommunications engineers, network architects and test laboratories
• Hardware and storage manufacturers
• Standards developers, regulators and compliance assessors
• Technical writers, educators and system integrators needing unambiguous unit definitions

Related standards

• ISO/IEC 80000 series (Quantities and units)
• SI Brochure (BIPM) and ISO/IEC Directives for unit and notation conventions

Keywords: IEC 80000-13, quantities and units, information science and technology, bit, octet, byte, binary prefixes, transfer rate, bit rate, erlang, baud, SI units.

Standards Content (Sample)

FINAL DRAFT
International
Standard
IEC/FDIS 80000-13
ISO/TC 12
Quantities and units —
Secretariat: SIS
Part 13:
Voting begins on:
2024-10-11
Information science and technology
Voting terminates on:
Grandeurs et unités —
2024-12-06
Partie 13: Science et technologies de l'information
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
This draft is submitted to a parallel vote in ISO and in IEC.
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
IEC/FDIS 80000-13:2024(en) © IEC 2024

FINAL DRAFT
IEC/FDIS 80000-13:2024(en)
International
Standard
IEC/FDIS 80000-13
ISO/TC 12
Quantities and units —
Secretariat: SIS
Part 13:
Voting begins on:
Information science and technology 2024-10-11
Voting terminates on:
Grandeurs et unités —
2024-12-06
Partie 13: Science et technologies de l'information
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2024
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
This draft is submitted to a parallel vote in ISO and in IEC.
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
IEC/FDIS 80000-13:2024(en) © IEC 2024

© IEC 2024 – All rights reserved
ii
IEC FDIS 80000-13 © IEC 2024 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
QUANTITIES AND UNITS –
Part 13: Information science and technology

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC Publication(s)"). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC and ISO draw attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC and ISO take 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, IEC and 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
https://patents.iec.ch or www.iso.org/patents. IEC and ISO shall not be held responsible for identifying any or all
such patent rights.
IEC 80000-13 has been prepared by IEC technical committee 25: Quantities and units in close
cooperation with ISO/TC 12 Quantities and units. It is an International Standard.
This second edition cancels and replaces the first edition published in 2008. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) addition of new prefixes for binary multiples.

– 4 – IEC FDIS 80000-13 © IEC 2024
The text of this International Standard is based on the following documents:
Draft Report on voting
25/XX/FDIS 25/XX/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English .
A list of all parts in the ISO 80000 and IEC 80000 series, published under the general title
Quantities and units, can be found on the ISO and IEC websites.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IEC FDIS 80000-13 © IEC 2024 – 5 –
INTRODUCTION
0.1 Tables of quantities
In most cases, only one name and only one symbol for the quantity are given; where two or
more names or two or more symbols are given for one quantity and no special distinction is
made, they are on an equal footing. When two types of italic letters exist (for example as with
J and θ; φ and f; a and a; g and g), only one of these is given. This does not mean that the
other is not equally acceptable. It is recommended that such variants should not be given
different meanings. A symbol within parenthesis implies that it is a reserve symbol, to be used
when, in a particular context, the main symbol is in use with a different meaning.
0.2 General
The names of units for the corresponding quantities are given together with the international
symbols and the definitions. These unit names are language-dependent, but the symbols are
th
international and the same in all languages. For further information, see the SI Brochure (9
edition 2019, updated in 2022) from BIPM and ISO 80000-1.
The units are arranged in the following way:
• The coherent SI units are given first. The SI units have been adopted by the General
Conference on Weights and Measures (Conférence Générale des Poids et Mesures,
CGPM). The use of coherent SI units, and their decimal multiples and submultiples formed
with the SI prefixes are recommended, although the decimal multiples and submultiples are
not explicitly mentioned.
• Some non-SI units are then given, being those accepted by the International Committee for
Weights and Measures (Comité International des Poids et Mesures, CIPM), or by the
International Organization of Legal Metrology (Organisation Internationale de Métrol ogie
Légale, OIML), or by ISO and IEC, for use with the SI. Such units are separated from the SI
units in the item by use of a broken line between the SI units and the other units.
0.3 Remark on units for quantities whose dimensional exponents are all equal
to zero
The coherent unit for any quantity whose dimensional exponents are equal to zero is the number
one, symbol 1. When the value of such a quantity is expressed, the unit symbol 1 is generally
not written out explicitly. Quantities that are ratios of quantities of the same kind (for example
length ratios and amount fractions) have the option of being expressed with units (m/m, mol/mol)
to aid the understanding of the quantity being expressed and also allow the use of SI prefixes,
if this is desirable (μm/m, nmol/mol).
EXAMPLE 1
Refractive index n = 1,53 × 1 = 1,53
Prefixes shall not be used to form multiples or submultiples of this unit. Instead of prefixes,
powers of 10 are recommended.
EXAMPLE 2
Reynolds number Re = 1,32 × 10
0.4 Numerical statements in this International Standard
The sign = is used to denote "is exactly equal to", the sign  is used to denote "is approximately
equal to", and the sign:= is used to denote "is by definition equal to".

– 6 – IEC FDIS 80000-13 © IEC 2024
QUANTITIES AND UNITS –
Part 13: Information science and technology

1 Scope
This document specifies names, symbols and definitions for quantities and units used in
information science and technology. Where appropriate, conversion factors are also given.
Prefixes for binary multiples are also given.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
The names, definitions and symbols for quantities and units of information science and
technology are given in Table 1 on the following pages.

IEC FDIS 80000-13 © IEC 2024 – 7 –

Table 1 – Quantities and units in information science and technology
Item No. Quantity Unit Remarks
Name Symbol Definition Name Symbol
13-1 traffic intensity A number of simultaneously busy  1 E corresponds to the occupancy of one resource.
resources in a particular pool of
erlang E The name "erlang" was given to the traffic intensity
resources
unit in 1946 by the International Telephone
Consultative Committee (CCIF), in honour of the
Danish mathematician, A. K. Erlang (1878-1929), who
was the founder of traffic theory in telephony.
See IEV 715-05-02.
13-2 traffic offered intensity A traffic intensity (item 13-1) of the traffic  1 E corresponds to the occupancy of one resource.
o
that would have been generated by the
erlang E See IEV 715-05-05.
users of a pool of resources if their use
had not been limited by the size of the
pool
13-3 traffic carried intensity, Y traffic intensity (item 13-1) of the traffic  1 E corresponds to the occupancy of one resource.
traffic load served by a particular pool of resources
erlang E General practice is to estimate the traffic intensity as
an average over a specified time interval, e.g. the
busy hour.
See IEV 715-05-04.
13-4 mean queue length L, (Ω) time average of queue length one 1 For the unit one, see the Introduction.
See IEV 171-02-34.
13-5 loss probability B probability for losing a call attempt one 1 For the unit one, see the Introduction.
13-6 waiting probability W probability for waiting for a resource one 1 For the unit one, see the Introduction.
−1
13-7 call intensity, λ number of call attempts over a specified second to the See IEV 715-03-13.
s
calling rate time interval divided by the duration power of
(ISO 80000-3:2019, item 3-9) of this minus one
interval
inverse
second
−1
13-8 completed call intensity μ call intensity (item 13-7) for the call second to the For a definition of the complete call attempt, see IEV
s
attempts that result in the transmission power of
715-03-11.
of an answer signal minus one
inverse
second
– 8 – IEC FDIS 80000-13 © IEC 2024

Item No. Quantity Unit Remarks
Name Symbol Definition Name Symbol
13-9 storage capacity, storage M amount of data that can be contained in one 1 For the unit one, see the Introduction.
size a storage device, expressed as a number
bit bit The specified data elements depend on the
of specified data elements
organization of the storage device, for example,
octet o
binary elements (also called "bits"), octets (also
called "bytes"), words of a given number of bits,
byte B
blocks. A subscript referring to a specified data
element can be added to the symbol.
EXAMPLES:
storage capacity for bits, M
bit
storage capacity for octets, M or M .
o B
For registers, the term "register length" is used with
the same meaning.
Although in this context the designation "bit", symbol
bit, is not really a unit, it is often used like a unit, e.g.
M = 32 000, where the unit one is implicit, is often
bit
written as M = 32 000 bit. Similarly, although the
designation octet or byte, symbols o and B,
respectively, are not units, they are often used like
units, e.g., M = 4 000 or M = 4 000, where the unit
o B
one is implicit, are often written M = 4 000 o or
M = 4 000 B.
When used to express a storage capacity or an
equivalent binary storage capacity, the bit and the
octet (or byte) may be combined with SI prefixes or
prefixes for binary multiples.
In English, the name "byte", symbol B, is used as a
synonym for "octet". Here, "byte" means an eight-bit
byte. However, "byte" has been used for numbers of
bits other than eight. To avoid the risk of confusion, it
is strongly recommended that the name "byte" and
the symbol B be used only for eight-bit bytes.
The symbol B for byte is not international and is not
to be confused with the symbol B for bel.

IEC FDIS 80000-13 © IEC 2024 – 9 –

Item No. Quantity Unit Remarks
Name Symbol Definition Name Symbol
13-10 equivalent binary storage M M = lb n one 1 For the unit one, see the Introduction.
e e
capacity
bit bit The minimum storage capacity of a bit-organized
where n is the number of possible states
storage device which would contain the amount of
of the given device
data in the given storage device is equal to the
smallest integer greater than or equal to the
equivalent binary storage capacity.
When used to express a storage capacity or an
equivalent binary storage capacity, the bit may be
combined with SI prefixes or prefixes for binary
multiples (see Clause 4).
In this context, “bit” is a special name as well as
symbol for the coherent unit one. For the unit one,
see the Introduction.
−1
13-11 transfer rate r, (ν) quotient of the number of specified data second to the The symbol ν is the Greek letter nu.
s
elements transferred in a time interval by power of
A subscript referring to a specified data element can
the duration of this interval minus one
be added to the symbol.
inverse
EXAMPLES:
second
digit rate, r or ν (see IEV 702-05-23 and IEV
d d
digit per
704-16-06);
second
transfer rate for octets (or bytes), r , r , v , or v ;
o B d B
binary digit rate or bit rate (item 13-13).
octet per o/s, B/s
second, byte
In English, the name "byte", symbol B, is used as a
per second
synonym for "octet". Here "byte" means an eight-bit
byte. See remarks in item 13-9.
The octet per second (or byte per second) may be
combined with prefixes, for example kilooctet per
second, symbol ko/s (or kilobyte per second, symbol
kB/s).
– 10 – IEC FDIS 80000-13 © IEC 2024

Item No. Quantity Unit Remarks
Name Symbol Definition Name Symbol
13-12 period of data elements, T T = 1 / r where r is the transfer rate second s A subscript referring to a specified data element can
(item 1
...