Monday, July 24th, 2017

Your Library in Dewey

We’ve made a handy graphical way to see how your library matches up with Dewey®.

The Dewey Decimal System®, also called the Dewey Decimal Classification® (DDC)—called the “Melvil Decimal System” on LibraryThing for legal reasons—is the classification used by most public libraries, especially in the US. First developed in 1876, it divides the world into ten major categories 0-9. Each of these are further subdivided 0-9 again, twice, yielding a number between 000 and 999. Further division is accomplished by adding a decimal point (.) and adding more decimals. It’s imperfect, but it’s simple—and it’s everywhere.

Here’s what it looks like on the top level. I have a lot of history and religion. True enough.

Screenshot 2017-07-24 12.00.11

Here’s one level down. Did someone say “occult”?
Screenshot 2017-07-24 11.56.00

Here’s what it looks like posted to Facebook:
Screenshot 2017-07-24 12.04.58

“Dewey,” “Dewey Decimal,” “Dewey Decimal Classification” and “DDC” are registered trademarked of OCLC, an Ohio-based library cartel.

Labels: classification, new features


  1. Jason Riedy says:

    Any way to share these bar graph images on “social” (yet increasingly anti-social) media?

    • Loranne says:

      As mentioned in the blog post above: “You will also find that, if you post your page to Twitter or Facebook, it will post a full-sized graph–a hint of a feature that’s coming more generally soon.” So, all you need to do is copy/paste the link to your Dewey chart on social media, and it will show this image.

  2. Mary Capps says:

    Alas, no graphic shows when posted on Facebook – just a large blank area.

  3. RaucousRain says:

    This is very cool …. thanks!

  4. Luchtpint says:

    Another nifty LT thingy. Just what I wanted.

    Yippee Yay ! Keep up the good work.

  5. jhawn says:

    This will be very helpful to me. I have so many books that I use the Dewey Decimal System to help organize them – especially when I make the grandkids help pickup. I am still in the process of doing this and have been using the OCLC website to get the codes ( They don’t have them all and sometimes I find it difficult to understand why a particular code is chosen.

  6. allmccarters says:

    This is very interesting, but I’m curious what information you use to determine the classification. The catalog record, or my comments or tags? For example, my library shows only 23 biographies, but I believe the number is closer to 90. Please explain. Thanks!

    • Loranne says:

      This chart is based on the data for each individual book’s Dewey Decimal number—if that’s part of your book’s record. If not, it accounts for DDC info attached at what we call the “work level“. Each book on LT corresponds to a work page, which represents all copies of a book, regardless of edition, publication date, title variant, or language. Essentially, unless you have the sole copy of a book that exists on LibraryThing, and you cataloged it from a data source that does not include DDC data, our system makes a calculation based on all other copies/data sources—a best guess as to a valid DDC number.

      If you have further questions, please email us at and we’ll be happy to help you from there!
      If y

  7. allmccarters says:

    Correction, your analysis shows only 5 biographies, 92x.

  8. Rob Kinnon-Brettle says:

    How does it know the Dewey if I don’t input the Dewey? I don’t have a Dewey Catalogue in which catalogue my collection.

    • Loranne says:

      It might be pulled in based on the data source you used when cataloging. Barring that, the system makes a best guess at a Dewey number based on other members’ data from folks who’ve added the same book. If you’re the only one with a given book on LT, and your data source for cataloging it did not have Dewey info, it will likely be blank and not calculated.

      You can see your Dewey data in Your Books by adding the “Dewey Decimal” field to one of your Display styles (look under “Classification” on the right-hand menu). Please email us at (or post on Talk) if you have any further questions.

  9. Frans says:

    I’ll just throw it out there that the Universal Decimal Classification is used as the main system in 34 countries (source). Just in case there’s some legal advantage to be found there. ;-)

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