Johnny Decimal?

Johnny Decimal is a fantastic system. To be honest it channels the name Johnny Silverhand for me. This name is quite popular right now thanks to Cyberpunk 2077. I am astounded that some of the niche stuff we were doing is quite mainstream - Cyberpunk 2020 is one of them.

Aanyway, I am digressing! Johnny Decimal is a folder organization system that’s both convenient and simple to use and setup. If you want to see the source itself please click here to move to its own page.

It has three main governing rules:

  1. 10 Areas
  2. 10 Categories in each area
  3. 99 Ids in each category.

When written/heard like this it sounds complex, right? Let me give my own example. I have a Library area, in this library I have Fiction, NonFiction, IT and Russian categories. In fiction I have general, science fiction and techno-thrillers:

Area: Library Category: Fiction Id: General

But… where is the number? Where are the DECIMALS?!

Enter the decimal!

System works like this. I dedicate numbers 30-39 to Library (10-19 is for IT stuff, 20-29 is for Academic stuff and so on). The numbers doesn’t make that Area better or worse than others.

Then I create my Fiction category and take the number 31. Now any folder I open inside this category will start with 31.. I decided to separate my sci-fi & technothrillers from my general fiction library so I have three ids here:

  • 31.01 - General
  • 31.02 - Science Fiction
  • 31.03 - Techno-Thrillers

Now, I am digressing from the JD orthodoxy and do my exception here. Normally you SHOULDN’T have another folder in an id folder. But because I am using Calibre as my library manager, I use these id folders as virtual devices - and Calibre does it by foldering. So this is my only deviation from the system.

What good is it?

It is good because you can finally have a mental structure in your mind. When I hear category 12 (for example) I will instantly know that it is not related to my library because it starts from the number 30. With this system I have a theory about my filing cabinet. Whatever I get/download/save should find its place in this system.

On top of that it gives me the feeling the YNAB system has - You Need A Budget, a fantastic app if you are into personal budgeting. You roll with the punches. Currently I am occupying 5 main areas, and none of my areas are full! When and if I need another area, I am free to do so. When and if I need another category in an area, I can knock myself out.

Finally, it works so sweetly with grep and find under Linux.


There are two caveats and warnings I can give to you. First, remember that this is a FILE organization system. I thought about it a lot and for organizing notes I find its system stifling. For example what happens if I want to store my book notes? Should I create a Book Notes area, under it Philosophy category and merrily create a folder for each book I read? This doesn’t look that good to the eye and to be honest I find it stifling and worry about “What happens when I read more than 100 books?” (and I do have and read more than 100 books).

Solution? I came up with dedicating 11.01 to my book notes in a Cherrytree file for philosophy, 12.01 for Sociology and so on. Neat thing is, if I want to check my IR notes (for example) I know its id will be 01 and it will be on the tenth space.

Second, give yourself time. The system is deceptively simple but when you think about applying it you will encounter problems specific to your files,usage and responsibilities. Write your versions, think about your areas, categories and ids and THEN apply it. I have this suspicion that when done right, this system will create aesthetically pleasing folders where you can find whatever you look for with ease.

Thank you!