Good Numbering Practices


Hello, good people of the world! In industry, we have a lot of cause to number things. We number equipment, documents, instruments, SOPs, processes, etc. so that they can be easily identified and referenced. What are the cGNPs (current Good Numbering Practices)?

  1. Identification numbers should be unique. This is critical and fundamental. Whatever you’re numbering, each item in the collection must have a unique number so that it can be identified and not confused with something else. This may sound trivial, but it can be difficult when a collection gets large if you don’t have a robust way of managing numbers (e.g. a relational database).
  2. The numbering scheme should be scalable, meaning adding additional numbers should not cause undue burden, even if  you have to add a large amount.
  3. The numbering scheme should be informative. You want the number to immediately tell a person something about the item being numbered. A sequential number is meaningless. A random number even worse.
  4. The numbering scheme should be reasonable length. You want to convey as much information as possible in the number without making it too long. What’s too long? Any more that 15-20 characters is getting too long.
  5. Most importantly: define your numbering scheme. Make it easy for anyone to know what each part of your numbering scheme means, and how new numbers are determined. Your numbering scheme should not be mysterious!

Examples of good numbering schemes I’ve seen in industry:

  • For equipment: T-0310-1, where T stands for tank, 03 is the building number, 10 is a functional area (e.g. fermentation, purification, etc.) defined in an SOP, and 1 is a sequential number
  • For validation documents: AREA-TYPE-YYxxx.00 where AREA is the functional area, TYPE is the document type (.e.g. IOQ, PQ), YY is the two-digit year, xxx is the next sequential number for the unique AREA, TYPE, YY combination, and 00 is the revision (starting at 00 for initial version).

What numbering schemes do you like? Leave a comment below and please share this post with whomever you think would benefit.

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