The Johnny Decimal system

Discover the Johnny Decimal system and organize anything with grace

The Johnny Decimal system

In this article, I will introduce the Johnny Decimal system for organizing digital information.

This content is part of my Obsidian Starter Kit


While the LIFT principle provides a clear set of principles to avoid feeling overwhelmed and quickly find what we need, the Johnny decimal system provides a “framework” for better organizing our information.

As we will see, just like the PARA method, the Johnny Decimal system can be used across tools and platforms, which makes it another excellent tool to add to your information/knowledge management toolbox.

How the Johnny Decimal system works

The Johnny Decimal system is a simple three-step process to organize information:

  1. Divide everything you want to organize into 10 areas (at most!)
  2. Within each area, divide your content into 10 categories (at most!)
  3. Assign a unique number to each area and category

During the first step, you need to:

  • Make sure that every area is really different. You don’t want any overlap between those, although it isn’t always easy (or possible!)
  • Choose a unique name for each area

One of the core ideas of this system is to group related information together.

With the Johnny Decimal system, you can create at most 10 areas, each containing at most 10 categories. That’s it. The reason for this limitation is to keep things simple and manageable.

The first step of the process aims to force you to broadly organize your content. The limit on the number of areas is there to force you to keep things simple. The fewer folders you have, the easier it will be to identify and locate (cfr LIFT principle) what you are looking for or want to store.

The second step is key. Categories are where your content actually lives. Each category should hold very specific information/content.

Finally, the last step has multiple purposes:

  • First, it makes it easier to identify what you’re looking at, which means that you gain time when going through the structure, either to find or file information. Once you recognize the numbers, you don’t even need to read the names anymore
  • Second, it allows you to organize categories logically, rather than alphabetically, which allows you to put what you need most often/what makes more sense on top
  • Third, it makes it easy to see where information is NOT supposed to be

The Johnny Decimal numbering system

With the Johnny Decimal system, numbers are always structured.

For areas:

  • two-digit code
  • start at 10
  • increase by 10 (e.g., 10, 20, 30, ...)

For categories:

  • two-digit code
  • start at area number + 1 (e.g. 11 for area 10)
  • increase by 1

You may also assign a unique number to each item within a category. If you do, then you should use the following form:

<category identifier>.<item identifier> <name>


  • <category identifier> is the two-digit code of the category
  • a decimal dot separates the category number from the item id
  • <item identifier> is a two-digit code starting with 01 and increasing by 1 (e.g., 02, 03, 04, ...)
  • <name> is the name of the item


  • You should not create folders below the categories
  • Always use the two digits for consistency, and to help your computer sort things correctly


  • Use the lower numbers for the most important/relevant/often used information (e.g., 10 for an area you use daily and 90 for an area you only rarely need)
  • Keep your area and category names clear and concise
  • Create (and maintain!) an index of your areas and categories, as recommended here; especially if you use the system in multiple places. That way you’ll ensure consistency across all of those

Note that you could also use Johnny Decimal numbers for your PKM notes. I personally choose not to, but know that it’s a possibility, as explained here.

Benefits of using the Johnny Decimal system

First and foremost, the Johnny Decimal system brings structure to your information:

This alone is a great reason to use this system. It organizes everything clearly, and consistently.

The system forces you to restrict yourself to a limited number of areas and categories, which helps clearly organize your content without feeling overwhelmed by complexity and depth. As mentioned before, this helps a lot to locate and identify information. As mentioned on the official Website, “nothing is more than two clicks away”. It’s easy to find your way, and hard to get lost.

It makes it easy to tell people where to look for things. Imagine calling your partner to ask for a file. If you use the Johnny Decimal system, then you can easily explain where to go to find what you need.

Using the Johnny Decimal makes it easier to search for specific information. Just type in the coordinates (e.g., 10.01) to find related content.

Given that the Johnny Decimal system uses numbers, we can order everything in the most logical manner. Without this system, we often rely on the alphabet, which makes it much harder to order things logically.

Just like the PARA method and the LIFT principle, the Johnny Decimal system can be used in most tools and on most platforms. You can use it for your file system, your Google Drive, your OneDrive, at work, for your e-mail, in your note-taking tool, etc.

Going further

If you want to further explore Personal Knowledge Management, then take a look at starter kit for Obsidian. It will give you a solid starting point for your note-making efforts.

Also check out my Personal Knowledge Management Library. It’s a huge collection of resources (articles, books, videos, YouTube channels, and a lot more).

By the way, I publish a weekly newsletter about PKM, note-taking, lifelong learning, and more!

If you find PKM interesting (I really hope you do!), then you might want to join our community.


In this article, I've introduced the Johnny Decimal system. It's a simple, but very effective system to organize your information across tools and platforms. You can combine this system with the PARA method to organize just about anything.

That's it for today! ✨


About Sébastien

Hello everyone! I'm Sébastien Dubois. I'm an author, founder, and CTO. I write books and articles about software development & IT, personal knowledge management, personal organization, and productivity. I also craft lovely digital products 🚀

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