How do I read and interpret an IPC symbol?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

To read and interpret an International Patent Classification (IPC) symbol, follow these steps:

1. Identify the section letter (A-H)
2. Read the two-digit class number
3. Note the subclass letter
4. Interpret the group/subgroup numbers

For example, in the symbol A 01 B 1/24:

• A: Section (Human Necessities)
• 01: Class
• B: Subclass
• 1/24: Group (Main group 1/00, subgroup 24)

The MPEP states: Any third or fourth digit after the oblique stroke is to be read as a decimal subdivision of the second or third digit, respectively; e.g. 3/426 is to be read as “three slash forty-two point six”, not three slash four hundred and twenty six and is to be found after 3/42 and before 3/43. This helps in understanding the hierarchical structure of the classification.