My patent specification has around 20 chapters and each chapter has multiple drawings.

My drawings are numbered like this. FIG. 1A, FIG. 1B, FIG. 2A etc. i.e. If Chapter 2 has only 2 drawings, then the drawings will have numbers like FIG. 2A and FIG. 2B.

And I have numbered each unique feature like 202, 204 etc. This kind of numbering works fine when you don't have more than 50 unique features.

My chapter 6 has around 20 drawings and more than 50 unique features. So I would like to name the feature numbers like 6A02, 6A04 etc.

Is this accepted or I have to follow some standard for diagram numbers?

  • I'm a little confused aren't there 100 possibilities between 200 and 299? Features can and should be shared between different figures they are shown on.
    – Eric S
    Jul 21, 2019 at 18:44
  • @EricShain Yes, but i'm using even numbers. Many patents I have seen follow that structure. I'm not sure why. Jul 21, 2019 at 19:07
  • Maybe you should ask that question. I don't think there is any reason to limit you to even numbers other than it gives you room to add another feature if you forgot one.
    – Eric S
    Jul 21, 2019 at 19:14

2 Answers 2


The MPEP says reference characters are preferably numerical. Patent applications do not usually have "chapters" and there is no need to invent a convention like that. As mentioned, even numbers let you add a number later without worrying about re-numbering but renumbering would not be needed anyway. That is not true of drawings - they need to be in order. There is no requirement that says a reference 500 can't appear on a figure full of references in the 200's. If you have a "2nd embodiment" and want to have all of the reference designators remind the reader of that, feel free to start with 2000 rather than 200. MPEP on drawings

  • A link to the MPEP page can be very helpful. Jul 21, 2019 at 21:20

The more complicated we make to understand drawings then there are high chances that even the examiner will get confused and issue an office action on it. The basic necessity of patent application is it should enable a person skilled in the art to understand.

Using numbers than characters are preferable.

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