I’ve spent a long time wondering how the Hogwarts library is organised and, when I couldn’t find anything online, I decided to take matters into my own hands. Check out this video (transcript below) for my results!


It should come as no surprise that I’m a pretty big fan of the Harry Potter universe (especially the books) and one of the most intriguing parts of the books, to me, at least, is the Hogwarts School Library. We see Harry, Ron, and Hermione, especially Hermione, use the Library a lot throughout the series – whether it’s looking up Nicholas Flamel, or doing legal research to save a hippogriff, or just doing their homework – whenever we’re in the library with these three, I always kind of wonder what the Library is like. We get an idea of the atmosphere and what’s in the Library from the books, and the films and the games offer a few different perspectives of how it might be laid out and what it might actually physically look like, but more interesting to me is how do people know where to find what they’re looking for? How to students and teachers know to get what they want? And how do Librarians know where to put stuff once it’s been taken off the shelf?
The core of these questions really is “How is the Hogwarts School Library organised?” I mean, do they use Dewey? You’re probably familiar with the Dewey Decimal Classification System; it’s the one most widely used in the English speaking world, where every item in a library’s collection is assigned a number from 001 to 999.99999… based on that item’s subject, or class, and sub-subject, or sub-class. So an example here is this book: Australian Bird Names, a Complete Guide. It’s been given the Dewey number 598.0994, as you can see in this picture:

The catalogue record of Australian Bird Names showing the Dewey Number

I’ll take you through this:

500 is the science section, so this is a book about science.

590s is zoology, so we know that this is a zoological book.

And 598 is birds, so we know that this is a book about birds.

And that’s roughly how Dewey works. It takes an item, looks at what it’s about, and then assigns a number based on that. The .0994 adds an extra layer of specificity. Not all books have the .0994, some have different decimal points, some don’t have any decimal points. In this case, .0994 means Australia, so we can look at this call number, this Dewey number, and go “well, we know that’s a book about Australian birds”. Done.
So if we were to apply the Dewey Decimal System, or DDC, to the Hogwarts School Library, what would it look like? Well, much like this book: The Element Encyclopedia of Vampires, every item in the Hogwarts School Library would start with 13 (pronounced “one three”, not “thirteen”). In this case we’ve got 133. And this is because, in Dewey, the occult is given the range 130 to 139, and pretty much everything in the Hogwarts School Library is about the occult – it’s all about magic. So using Dewey to organise the Hogwarts School Library is not going to be useful. They have 10,000 books, if you’ve got every single book starting with the same two characters, 13, it’s unusable, so no, we won’t be using Dewey to organise the Hogwarts School Library. We won’t be using any Muggle created system, I don’t think. Not Library of Congress, not Metis, not BISAC, because they’re all too mundane. What I think the Hogwarts School Library, and the library at the Ministry of Magic – because there has to be a library at the Ministry of Magic, right? I think both of these libraries use the same system, which we’re going to tentatively call the British Wizarding Library Classification System. And today, we’re going to see if we can build that system.
Just a bit of a massive caveat before we start. While I’m a librarian, I’m not a cataloguing librarian. So this is going to be an interesting experiment. I don’t know if it’s going to work, and I don’t even know if my methods are going to be good. Let me know in the comments if you are a cataloguing librarian and if I have massively messed this up. I’d be really interested in hearing from someone who has experience in this field. Anyway.

Subjects and classes

As with Dewey, most library classification systems organise their collections by subject or class. So we’re going to start with a list of Hogwarts subjects. We know from the books and films that first year Hogwarts students are required to take:

  • Transfiguration
  • Charms
  • Potions
  • History of Magic
  • Defence Against the Dark Arts
  • Astronomy, and
  • Herbology

Flying is also part of the first year syllabus, but we only ever see one lesson. So let’s add it anyway. And now we’re going to add the electives introduced in years 3 through 7:

  • Arithmancy
  • Muggle Studies
  • Divination
  • Study of Ancient Runes, and
  • Care of Magical Creatures

Hermione famously takes all the subjects in book number 3, leading to hilarious time travel hijinks. JK Rowling also states that there might be some extra subjects taught if there’s enough demand, such as Alchemy and Apparition, which we actually do see in book number 6. Then there’s all the extra curricular activities listed on the Harry Potter Wiki which pulls references and mentions from the books the games, and the films.

  • Advanced Arithmancy Studies
  • Ancient Studies
  • Art
  • Frog Choir
  • Ghoul Studies
  • Magical Theory
  • Music
  • Muggle Music, and
  • Orchestra

Xylomancy is also mentioned on the Wiki, but that’s a branch of Divination that uses twigs. Get it? It’s a branch of Divination that uses twigs. It’s taught at Ilvermorny, the North American school, and not at Hogwarts, so we’re going to put it in with the rest of Divination. Which brings us to the next step in this process: simplifying this big long list of subjects into something slightly more manageable.

Simplify, simplify, simplify

Now, as with Xylomancy fitting into Divination, a lot of these subjects will fit into each other or into another, larger, unnamed class. So for example: Care of Magical Creatures and Ghoul Studies would probably go into a class called Magical Creatures. This is also where we’d find information about dragons, hippogriffs, blast-ended skrewts and also, unfortunately, more sentient and humanoid creatures like mer-people, centaurs, giants, house elves, and probably goblins. Because wizards are kind of terrible.
I created a spreadsheet to do this. I also had a look a few things up to find out what they were, exactly, because some of these are kind of obscure. Did you know that Arithmancy is Hermione’s favourite subject, but it’s basically just Divination, which is Hermione’s least favourite subject, plus math? Anyway here is our simplified list of subjects:

  • Alchemy
  • Art and Music
  • Defence Against the Dark Arts
  • Divination
  • Games, Sports, and Physical Activities
  • Languages
  • Magical Creatures
  • Muggle Studies
  • Natural Magic
  • Potions
  • Thaumaturgy
  • The Wizarding World

From 25 down to 12, that’s a pretty good start, but not perfect. It’s just a good start. Thaumaturgy is the working of miracles or doing magic – I borrowed that one a little bit from Terry Pratchett’s Discworld series – and includes Charms, Transfiguration, as well as Magical Theory.
I really struggled with two of these subjects: Alchemy and Defence Against the Dark Arts. Alchemy, because we just don’t know a lot about it in the Wizarding World, whether it would fit into one of the other classes. I thought about putting it in potions, but I decided to make it its own class. Defence Against the Dark Arts is an interesting one. Because it’s such a multidisciplinary field, it pulls information from almost every other subject, so it belongs in its own class as well. But I can definitely see a reason for both Alchemy and Defence Against the Dark Arts to be moved into other classes.


Now we need some way of identifying each of these subject headings that’s easy and concise. We could just take the subject headings themselves and use that, but that’s not particularly concise. It’s not going to fit onto a spine label. We could also just take the first letter of the subject headings. The problem with that is that we’ll then have double ups which will be confusing and not easy. What I think we might do is borrow from Library of Congress classification system and use letters to represent different classes. But not English (Roman) letters we’re going to use Greek letter, because it wouldn’t be a Harry Potter Wizarding thing without some reference to the Ancient Greeks. Now I’m not going to create a hierarchy with this, and I’m not going to make each subject flow sort of naturally into another, like in Dewey; it’s more work and more refinement than I’m wanting to do right now. So let’s go down our new list of classes and assign each one a Greek letter:


We’re only using half the Greek alphabet at this stage, which gives us lots of room to expand, if we need to, at a later date. And we could just leave it at that, and then organise each book within each class alphabetically, so that Fantastic Beasts and Where to Find Them by Newt Scamander would come under η S (eta S), and that would work. Except that the Hogwarts School Library is quite large. It has quite a number of books, and I think it would be good to have more refinement. We don’t know how many ‘S’es there might be in that section, so we need to add more detail, much like in Dewey.We could divide each class into 100 sub-classes giving them a number just like in Dewey does. Or we could use the English alphabet to divide each class into 26 sub-classes.
Using numbers would give us 1200 total possible sub-classes, or using the alphabet give us 312 possible subclasses. I’m kind of leaning towards using the alphabet because it makes about as much sense as anything else in the Wizarding World, especially the money. We don’t have enough information about each subject taught at Hogwarts to really go into much further detail here, but we do know a bit about some subjects, like Divination. We know that Hogwarts students in Divination take:

  • Astrology – reading the stars and planets
  • Cartomancy – reading tarot cards
  • Crystal-gazing – looking into a Crystal ball
  • Dream interpretation – what it says on the box
  • Palmistry – reading someone’s palm
  • Tessomancy – reading tea leaves
  • General divination

There are more, but this will be for a start. What we can do with these Divination subjects is, much like the major classes, assign them a letter.

  • A – General divination
  • B – Astrology – reading the stars and planets
  • C – Cartomancy – reading tarot cards
  • D – Crystal-gazing – looking into a Crystal ball
  • E – Dream interpretation – what it says on the box
  • F – Palmistry – reading someone’s palm
  • G – Tessomancy – reading tea leaves

So if we wanted to find a copy of Unfogging the Future by Cassandra Vablansky, we would start looking in the δ (delta) section, for Divination, and then we would look under A because it’s a general textbook that covers all the subjects, and then let’s go with V for Vablansky. So δ A V, and we should find Cassandra Vablansky’s book.

And I think we’re done – we’re going to leave it there. It’s been an interesting exercise, and I think we’ve made a really got start into sort of thinking about how the Hogwarts School Library would be organised, and how we classify books within that. It’s far from perfect, and I think there’s definitely a lot of room for improvement, and I’d love to know what you think could be improved. In a future post, we’re going to talk about how the Hogwarts staff and students find what they need without memorising this whole system.

Organising the Hogwarts School Library

One thought on “Organising the Hogwarts School Library

  • 17/03/2018 at 9:53 pm

    There are typos in the video. This is why I should hire a proofreader.


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