What are examples of claim language that have been held to be indefinite regarding numerical ranges?

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.

The MPEP provides specific examples of claim language involving numerical ranges that have been held to be indefinite. These examples illustrate potential issues with clarity and definiteness in patent claims.

As stated in MPEP 2173.05(c): “Examples of claim language which have been held to be indefinite are:

• (A) “a temperature of between 45 and 78 degrees Celsius, preferably between 50 and 60 degrees Celsius”; and
• (B) “a predetermined quantity, for example, the maximum capacity.”

These examples demonstrate how the inclusion of preferred ranges or examples within a claim can create ambiguity about the intended scope of the claim. In such cases, it’s often recommended to move these preferences or examples to the specification rather than including them in the claim language.

It’s important for patent drafters to be aware of these examples to avoid similar issues of indefiniteness in their own claims involving numerical ranges or amounts.