NOTE: Both Michelle Howard, the author of this informative post, and Liz Cottrill and Emily Kiser of Living Books Library in Tennessee highly recommend using the Dewey Decimal System to classify and organize your books. You can use LibraryThing or Michelle’s library database or this OCLC site to find the most commonly used call number in the Dewey Decimal System for any given book.

From Michelle Howard of Children’s Preservation Library in Michigan and Living Learning Libraries in Florida:

We are so excited to hear about new libraries, and new librarians beginning to organize their collections so they can be harnessed to the fullest! I always say that news of a blossoming library is about the best news possible because so many children/teens will have their inner worlds opened up in a whole new way and their hearts inspired to worthy thinking and believing, something that few can experience with only the pulp too often on other library shelves which is at best useless, and at worst toxic. Super!

As for the Dewey Decimal system, I remember feeling confused and intimidated before learning it, but now, Mr. Melvil Dewey (not to be confused with the dreadful John Dewey) is one of the first people I want to meet in heaven, and how could a serious bibliophile not be there! 😉 (Just kidding….) Once we see that the numbers have meaning, and are not a sea of random digits, it all comes together beautifully.

Anyway, it really is good naming to include “Decimal” in the system, because it follows the natural break- down by tens, just like our fingers work. So, take “all knowledge” and divide it by ten. That gives you your first main categories, and once you know those (and only eight are often used), you’ve taken the first step: 

• 000s (Rarely used in youth libraries, so I won’t bog you down with details.)
• 100s (Again, rarely used in youth libraries.)
• 200s Religion
• 300s Government 
• 400s Language
• 500s Pure science (observing God’s creation)
• 600s Applied science (how “pure” science is harnessed) 
• 700s Art (and a bit of Recreation)
• 800s Literature
• 900s History and Geography 

Now, if you were to see a Dewey Decimal number (DD#), say 523, you would already know something HUGE about it…..that it is about pure science. You’re right! You know what the number (5) in the “hundred’s place” means, and that is a lot! 

Now, we can take those 500s, and break them into another set of ten, and that will give us each of the main fields within pure science: 

• 500s Miscellaneous 
• 510s Math
• 520s Astronomy 
• 530s Physics 
• 540s Chemistry
• 550s Earth Science
• 560s Paleontology (fossils, dinosaurs, etc.)
• 570s Biology
• 580s Botany (plants)
• 590s Zoology (animals) 

So, what is our book labeled 523 about? Yes, it has something to do with astronomy! Now, you may think that this is a lot to memorize, but I didn’t have to look up what I wrote just now. Because I am brilliant? Hardly…. But because once you work with the system for a very short time, the ORDERLINESS of the numbers gets into your head, and I am a “word” person too. Besides, it only takes a single chart nearby as a “cheat sheet” to help you get familiar with the numbers. Your first chart can be just the 100s; then move to a chart of the 10s within an important 100, etc., and by that time you “think” Dewey! I ordered a “flip file” from DEMCO (a main library supplier) so that my patrons could quickly orient themselves. 

When the DD system REALLY gets interesting is when you see the finer “patterns” of its tapestry, for you must remember that there is no randomness to the numbers (one more reason that I’m guessing, er, hoping, that Mr. Dewey will be in heaven). So, every time you learn a number, you are one step closer. For example, do you remember that the 500s are about pure science? Well….that “5” will carry that same meaning into other settings too. Let me give you an example… 

If we were to jump to the 900s, another HUGE section in a youth library, since it covers “History/Geography/People IN that History and ON that Geography (or ‘biography’),” it would look like this: 

• 900s General topics that span many periods, such as pirates or being stranded on a desert island or sea disasters, such as “Titanic”….
• 910s Geography (exploration, maps)
• 920s BIOGRAPHY  920 is the number for group biographies, like “Famous Kings.” 921 is for biographies of ONE person, so most group bios are either 920 or 922-9…..and this is where it gets interesting, see below.
• 930s Ancient History
• 940s Europe
• 941 Scotland & Ireland
• 942 England
• 943 Germany
• 944 France, etc….
• 950s Far East
• 960s Near East
• 970s North America The good ol’ USA happens to be 973.
• 980s South America
• 990s Other (Australia, New Zealand, North & South Pole), etc. 

Okay….I mentioned when we were peeking at the 920s that this is where the DD system gets interesting. You know that the 920s are about biography. And….drumroll, please….you remember that the 500s are about pure science……so…….guess what the 925s are?!?!?! YES!!!! Group biographies of pure scientists!!! (If it was a biography about a single scientist it would be at 921, and then under his/her last name, such as 921 EINSTEIN). So, you didn’t waste anything by learning that the 5 in the 500s stands for “pure science.” Oh…..but now you’re charging ahead of me! Now you’re not even waiting for me to get to tell you the next great part! You are right….Since the 520s are about astronomy, then 925.2 is group bios of astronomers, and 925.3 is group bios of physicists (because 530 was physics, and 925.4 is group bios of famous chemists because (540 was about chemistry), etc., etc. So, when you learn that the 520s are about astronomy, and that the 900s are history/geography/biography, and you learn that the 920s are the biographies in particular, it is not one bit hard to put it all together that 9 (human history)2 (biographies)5(pure science).2 (astronomy) are group bios about astronomers. See?!?!? 

Let me give you just one more beautiful example. Do you remember that we said that 973 is for the USA? (The 900 is for history/geography and the 70 is for North America, and the 3 was assigned to the USA…so 973, and they make easy-to-look-up charts showing the numbers assigned to each area.) Well, the “biology” of the US or the “rivers” of the US….will carry that “area code” 73 in them. So, once you know that -73 is the USA, you will spot that all over the place. And when you learn that -44 is for France, you will see it relate to French history (944), French painters (759.4), French cooking, French literature, etc. 

Long story short…..the numbers are not random. It is just like when you pick up the phone and could call anyone in the world….but then you start keying in a telephone number. It makes the vast possibilities come into focus by first directing your call to the correct area (using the area code), then to the right community (using the local prefix) and then to the right house (using the last four unique digits). Likewise, the Dewey Decimal system isn’t a random sea of numbers, but a few key MEANINGFUL components brilliantly woven together over and over again, so that your learning is quick and immediately effective. It will soon be like a second language to you because it is so logical. When you’ve learned just a few numbers, you’ll be shocked at how the whole things gels in your mind. Really! 

This post is part of our Ask The Librarian series, a Card Catalog Project. You can find more like this here. And, we would love to connect with you! You can find us on Facebook here.