DWPITM categorizes patent documents using a simple classification system for all technologies. This unique classification is consistently applied to all patents by Clarivate subject experts, enabling effective and precise searching in a particular area of technology. Patents are divided into three broad areas: Chemical, Engineering, and Electronic and Electrical Engineering. Each of these is then further divided into Sections and Classes which describe the technical area, or areas, covered by the patent.


Patents are divided into 21 broad subject areas or Sections. These are designated A-M (Chemical); P-Q (Engineering); and S-X (Electronic and Electrical).


These Sections are then further subdivided into classes. Each Class consists of the Section letter, followed by two digits. For example X22 is the Class designation for Automotive Electrics and C04 is the Class for all Chemical Fertilisers.
When used in combination with other online search terms e.g. a Keyword Search, these Classes allow you to precisely and effectively restrict your search to the relevant subject area.

For example, the otherwise ambiguous word “WARN” can be combined with X22 (Automotive Electrics) to retrieve only those references to automotive warning devices.

DWPI cross-classifies entries to ensure that all the patents of interest are retrieved when searching.

Brief details of the Sections are below, for full details please consult the DWPI Classification Guide.



Chemical patents currently covered by DWPI are selected for inclusion in one or more of the following twelve sections. All patents with the following IPCs are guaranteed to be included in the Chemical Patents Section: A01N, A21- A23, A61K, B01, B29, C, D, G21.
A – Polymers and Plastics
B – Pharmaceuticals
C – Agricultural Chemicals
D – Food, Detergents, Water Treatment and Biotechnology
E – General Chemicals
F – Textiles and Paper-Making
G – Printing, Coating, Photographic
H – Petroleum
J – Chemical Engineering
K – Nucleonics, Explosives and Protection
L – Refractories, Ceramics, Cement and Electro(in)organics
M – Metallurgy
N – Catalysts



Engineering patents currently covered by DWPI are selected for inclusion in one or more of the following 15 sections based upon the International Patents Classification (IPC) shown in brackets.
P – General
P1 Agriculture, Food, Tobacco (A01 excluding N, A24).
P2 Personal, Domestic (A41-A47).
P3 Health, Amusement (A61-A63, excluding A61K).
P4 Separating, Mixing (B02-B09).
P5 Shaping Metal (B21-B23).
P6 Shaping Non-metal (B24-B28).
P7 Pressing, Printing (B30- B32, B41-B44).
P8 Optics, Photography; General (G02, G03, G09, G10).

Q – Mechanical
Q1 Vehicles in General (B60).
Q2 Special Vehicles (B61-B64).
Q3 Conveying, Packaging, Storing (B65-B68).
Q4 Buildings, Construction (E).
Q5 Engines, Pumps (F01-F15)
Q6 Engineering Elements (F16-17).
Q7 Lighting, Heating (F21-F28, F41-F42).


These 15 Sections are broken down into 103 finer IPC-based Classes so as to narrow the subject matter into finer profiles for greater precision. Classification is made automatically by computer, based on the IPCs on the specification or, where not present, on DWPI-assigned IPCs.

Where a patent falls into more than one of the Sections P or Q, it will be placed in each, and may also occur in one or more of the Chemical Sections A-M or Electronic and Electrical Sections S-X.

Electronic and Electrical


Patents are divided into 21 broad subject areas or Sections. These are designated A-M (Chemical); P-Q (Engineering); and S-X (Electronic and Electrical). The Sections are used as the basis for both the DWPI  Classification and DWPI Manual Code systems.

Electrical and electronics patents covered by DWPI are selected for inclusion in one or more of the following six Sections:
S – Instrumentation, Measuring and Testing
T – Computing and Control
U – Semiconductors and Electronic Circuitry
V – Electronic Components
W – Communications
X – Electric Power Engineering


These six Sections are broken down into 50 Classes. These Classes are assigned according to the technical content as disclosed in the basic specification and take into account all the claims, particularly references to electrical applications, even when the main subject matter is chemical or mechanical in nature.
Where any patent specification falls logically into more than one Section of the Electronic and Electrical Classification it will be included in each of these Sections. Thus a patent involving a TV receiver line output transformer will be included in Classes V02 and W03 (Inductors and Transformers).