International Patent Classification

Vimal Kumar Varun
Scientist 'D'
Department of Scientific & Industrial Research
Technology Bhawan, New Mehrauli Road, New Delhi-110016
Internet: URL:


Describes the genesis, organization and Internet representation of International Patent Classification (IPC). Provides the outline of seventh edition and useful URLs related to it.

KEYWORDS: International Patent Classification, Patent Classification, Classification, Internet representation


The International Patent Classification, commonly known as the IPC, is based on an international multi-lateral treaty administered by World Intellectual Property Organization (WIPO). This treaty is called the Strasbourg Agreement concerning the IPC, which was concluded in 1971 and came into force in 1975. The Agreement aimed to overcome the difficulties caused by using diverse national patent classification system. The common classification system defined by the Agreement is applied to patent and utility model documents. The Agreement is open to States party to the Paris Convention for the Protection of Industrial Property. On January 1, 2000, forty-five States were party to the Strasbourg Agreement. However, the industrial property offices of more than 90 States, four regional offices and the International Bureau of WIPO under the Patent Cooperation Treaty (PCT) actually use the IPC.


The IPC is a hierarchical classification system comprising sections, classes, subclasses and groups (main groups and subgroups). Every subdivision of the IPC is indicated by a symbol and has a title. The IPC divides all technological fields into eight sections as shown in Table 1.

Each section is subdivided into classes whose symbols consist of the section symbol followed by a two-digit number. In its turn, each class contains one or several subclasses whose symbols consist of the class symbol followed by a capital letter, for example, A 01 B.

Table 1: Organization of the IPC




Human necessities


Performing Operations; Transporting


Chemistry; Metallurgy


Textiles; Paper


Fixed construction


Mechanical engineering; Lighting; Heating; Weapons; Blasting





Each subclass is broken down into subdivisions referred to as groups, which are either main groups or subgroups. Main group symbols consist of the subclass symbol followed by a one- to three-digit number, the oblique stroke and the number 00, for example, A 01 B 1/00.

Subgroups form subdivisions under the main groups. Each subgroup symbol includes the subclass symbol followed by the one- to three-digit number of its main group, the oblique stroke and a number of at least two digits other than 00, for example, A 01 B 1/02.

The title of a subgroup is preceded by one or more dots indicating the hierarchical position of that subgroup, i.e., indicating that each subgroup forms a subdivision of the nearest group above it having one dot less.

The Guide to the IPC

It provides detailed information on the subdivisions of the IPC. The main purpose of the Guide is to explain the layout and use of the IPC symbols, as well as the principles and rules of the IPC and its interpretation. It also gives advice on how to classify patent documents according to the IPC.

The appropriate IPC symbols indicated on each patent document (published patent applications and granted patents) are allotted by the national or regional industrial property office that publishes the patent document.

The Classification is indispensable for the retrieval of patent documents in the search for prior art. Such retrieval is needed by patent-issuing authorities, potential inventors, research and development units, and others concerned with the application or development of technology.

In order to keep the IPC up-to-date, it is continuously revised and a new edition is published every five years. The current (seventh) edition has came into force on January 1, 2000. The revision is carried out by the IPC Committee of Experts set under the Strasbourg Agreement. It consists of 8 sections, 120 classes, 628 subclasses and approximately 69,000 groups. The validity of different IPC editions is given in Table 2.

Table 2: Validity of the IPC Editions





September 1, 1968

June 30, 1974


July 1, 1974

December 31, 1979


January 1, 1980

December 31, 1984


January 1, 1985

December 31, 1989


January 1, 1990

December 31, 1994


January 1, 1995

December 31, 1999


January 1, 2000


The IPC exists in two authentic versions, English and French, which are published as printed publications by WIPO. Complete texts of the IPC are also prepared and published in other languages like Chinese, Czech, German, Hungarian, Japanese, Korean, Polish, Russian and Spanish by the respective industrial property offices.

The IPC is also published on the IPC: CLASS CDROM which was produced by WIPO with the participation of the German Patent and Trade Mark Office, the Russian Agency for Patents and Trademarks and the Spanish Patent and Trademark Office. IPC: CLASS which can be obtained from WIPO contains all IPC editions in English and French, the fourth to seventh editions in German, the fifth and seventh editions in Russian and Spanish, the catchword indexes in English, French, German, Russian and Spanish, revision concordance data and the IPC symbols data.

The authentic versions (English and French) of the sixth and seventh editions of the IPC are available on the WIPO Web site, permitting the user to browse the text of the Classification in order to find the relevant IPC symbols.


In the Internet presentation of the IPC, the index page includes a list of eight sections designated by letters A to H with the title of each section. After clicking on the relevant section, the contents of the section appear containing all classes and subclasses to which the section is subdivided. Having selected the relevant subclass, the user can navigate to its subdivisions and browse the groups included in the subclass until reaching the group covering the subject sought. The Internet version of the IPC also permits quick navigation in the text by using direct access ("Go!") to the relevant symbol of the Classification.

The hypertext links provided allow jumping from one language version (English or French) to the other by clicking on a flag located in front of main groups symbols. The similar manner of navigation is possible between IPC places interconnected by so-called references which represent phrases in brackets following a class, subclass or group title. Such a reference shows that the subject matter indicated by the reference is covered by the place (or places) referred to. A reference has the function of the limitation of scope or indication of precedence.

Having determined the essential characteristics of the technical subject which is being sought, it is necessary to locate in the IPC the appropriate place. To this end, a systematic approach should be adopted and followed step by step, i.e., the relevant section, class and subclass should first be identified and, then, the main group or the subgroup. It is particularly important to thoroughly read all the titles and explanatory notes, since they significantly affect the interpretation of the titles of subclasses, main groups and subgroups. The title of each subgroup must be read as being dependent upon, and restricted by, the titles of the higher level subgroups, the main group and the subclass. Bearing this in mind, it is necessary to select the lowest order (i.e., with the largest number of dots) subgroup which is still wide enough in scope to embrace all the essential characteristics of the subject in question.

For the uninitiated user, it is advisable to approach the Classification by using the official Catchword Index to the IPC. This publication contains thousands of catchwords representing specific technical terms used in patent documentation and technical literature, which are arranged in alphabetical order. Under the catchwords, the catchword phrases appear giving an indication of subject matter, which is designated by IPC symbols. It should be noted, however, that the Catchword Index in no sense replaces any part of the IPC and must not be read as modifying the effect of anything in the latter.


This edition has come into force on January 1, 2000. It should be noted that the patent documents bearing the symbols of the seventh edition has only started from January 1, 2000.

The seventh edition of the IPC is linked to the sixth edition in order to make information available as to how subject matter has undergone changed between the two editions as a result of the revision. This information is provided for revised groups by special buttons giving access to the data of the Revision Concordance List. After locating the relevant places in the seventh edition, the user can navigate to the places where the technical subject of interest was covered in the sixth edition.

To make automatic checking of the validity of IPC symbols allotted to patent documents possible, the IPC Valid Symbols List showing all symbols that exist in the seventh edition of the IPC is also available on the WIPO Web site.


Strasbourg Agreement

International Classification

Nice Classification /index.html

Locarno Classification /index.html

Vienna Classification /index.html

US Patent Classification System as of June 30, 2000 /explan.htm

European Patent Classification

Classification of Design Patents /examhbk/seven.htm

Examiner Handbook to the US Patent Classification System /examhbk/index.htm

Introduction to the IPC on the Internet

IPC 6th Edition /indexfrm.htm

General Information on the Seventh Edition of the International Patent Classification /index.htm

IPC 7 with Concordance Info

The Guide to IPC /guideeng.htm

Catchword Index to the IPC /ecw.htm

Introductory Manual to the IPC /index.htm

The First Twenty-Five Years of the International Patent Classification (1996) /index.htm

IPC: Glossary

Description and prices of the Seventh Edition of the IPC

IPC: CLASS CD-ROM /ipcclass.pdf

Attention ITT Readers

The Internet Edition of ITT, available at, comes out much before the publication of its print version. You may also browse the back issues from 1995 onwards.

Information Today & Tomorrow, Vol. 20, No. 2, June 2001, p.22-p.24