Arithmancy was a magical discipline in the wizarding world that dealt with the study of the magical properties of numbers.


The Definitive Glossary for Harry Potter

Arithmancy was one of the most logical disciplines taught at Hogwarts School of Witchcraft and Wizardry and resembled what Modern Science and Mathematics are like in Universities. The study of Arithmancy dealt with the magical properties of numbers and extensively used numerical charts and structures to determine predictable events of the future.

One could claim that Arithmancy was in fact a parallel to the reductive methods of Science, which, to some extent, do use Mathematics to determine the outcomes of controlled experiments. Unlike its ‘rival’ Divination, Arithmancy made use of logically accurate and well-informed steps to arrive at conclusions about the future instead of depending on vague details picked from guesswork and mundane things. While Numerology is also a discipline studied by muggles, Arithmancy, as seen in the Harry Potter universe with the application of real magic, is exclusively a field studied by witches and wizards. 


Arithmancy is quite an ancient discipline and probably as old as magic itself. The people who practiced this discipline were referred to as Arithmancers. It dealt with complex calculations made about future outcomes based on the magical properties of numbers. It is closely related to the discipline of Numerology. It was taught at Hogwarts as an elective after the students came to their third year as they had to pick several new subjects like Arithmancy, Ancient Runes, Divination, and Care of Magical Creatures. The textbook for Arithmancy was Numerology and Grammatica. One of the biggest differences between Divination as taught by Seers like Sybill Trelawney and Arithmancy is that while Divination makes use of interpreting something like tea leaves or glass globes and tries to recognize patterns that may predict the future, the latter purely depends on interpretations that are calculated reductively based on numerical values.

Also, Arithmancy is not unknown in the muggle world as some old Greek scholars like Agrippa and Pythagoras did study something in a similar vein. Also in the modern context of the discipline of Numerology, Arithmancy refers to a kind of Divination where a word or phrase is assigned numerical values by means of Greek isopsephy or an Aramaic or Hebrew gematria.


The term Arithmancy comes from the Greek word “Arithmos” meaning “number” and “Manteia” meaning “divination”. Arithmancy is sometimes also referred to aptly as number divination. Arithmancer is someone who “divines” from the “numbers”. 

Arithmancy in the Harry Potter Series

Arithmancy is an elective subject that third-years can take at Hogwarts School of Witchcraft and Wizardry. It ends up being Hermione’s favorite subject. Interestingly, in the movie adaptation of Harry Potter and the Prisoner of AzkabanHermione claims that Ancient Runes is her favorite subject. It dealt with many complicated number charts, and Harry once remarked that Arithmancy seemed terrible after he looked at a number chart lying around from Hermione’s homework. However, Hermione disagreed and claimed that she loved it. As opposed to the study of Divination which she loathes and eventually leaves after Professor Trelawney constantly belittles her ability in the Art of Seeing, Hermione grows into the discipline of Arithmancy. It is no surprise given how Hermione is intellectually stimulated by very logical disciplines and has a knack for picking up a lot of information and retaining it.

The third-year students are given a textbook for Arithmancy called Numerology and Grammatica which Hermione loses for a while in Harry Potter and the Prisoner of Azkaban. When she asks around for the book, Ron makes a joke about how he borrowed it for his bedtime reading. In the movie adaptation of Harry Potter and the Prisoner of Azkaban, there appeared to be two separate books – Numerology, by L. Wakefield and Grammatica, by M. Carneiro. Also, in Harry Potter and the Order of the Phoenix, for Christmas, Harry Potter gifts Hermione Granger the New Theory of Numerology written by Lukas Karuzos.

Strangely, both the discipline that Hermione detests (Divination) and the one she loves (Arithmancy) have a lot of similarities and tend to have common goals – that of determining outcomes of a situation or predicting the future. However, Hermione, being a more logical and serious student who favors sound reasoning, prefers the latter method as it reaches its results with a very systematic and sound process.

Magical Properties Of Numbers – The Concept of Emergence

While the muggle world may never be able to replicate the discipline of Arithmancy like the Harry Potter world does, the discipline of science that has been reductive through most of its existence has definitely undergone a paradigm shift to incorporate a slightly ‘magical’ touch to some of its results. While the Scientific Method still upholds the need to do Science in a rational way, there have been some findings that have, like Arithmancy brought about the magical properties of numbers.

One such approach is that of Emergence Theory. This theory concludes that the sum of all the parts of a whole is not just reductive to the whole. In the context of several scientific phenomena, this translates to there being some more subtle aspects that mere experiments cannot define. For example, consciousness in humans. While Advanced Medical Science and Neuroscience have made a lot of progress through Mathematics and other Natural Sciences in determining some certainties about human thought, there remain a lot of interesting phenomena like consciousness that simply cannot be explained reductively. Predicting the future even after creating highly detailed models is incomplete because complex systems like these tend to expand in complexity in very small time intervals, thereby making it almost impossible to claim that numbers do not have ‘magical’ properties.


What was Hermione’s favorite class?

Hermione’s favorite class was Arithmancy. Since Hermione was a prodigy and had a great interest in logical disciplines that could be mastered through focus and interest, she really liked how interesting Arithmancy was. Arithmancy dealt with calculating and plotting possibilities and predicting the future based on events, numerical data, and star charts gathered from the past. As opposed to Divination as taught by the seer Sybill Trelawney, which Hermione loathed for being an imprecise field of study, she loved Arithmancy despite how difficult it could be to study.

Who taught Arithmancy at Hogwarts?

Professor Septima Vector taught Arithmancy at Hogwarts. She was a very talented witch who probably also taught Advanced Arithmancy Studies at Hogwarts. She was considered to be a very strict teacher who gave her students plenty of difficult homework ranging from star charts to complicated numerical data. Despite this, Hermione really loved doing Arithmancy because of how challenging it was to her intellectual and inquisitive mind.

Is Arithmancy a real thing?

Yes, Arithmancy is a real thing. It is a discipline in the real world that deals with assigning numerical values to words and phrases and then figuring out complex connections that form between these terms. These connections and patterns are studied based on the properties of numbers. Arithmancy is a major discipline under numerology. Unlike the magical discipline of Arithmancy taught at Hogwarts, its real-world counterpart does not delve into predicting the future based on the magical properties of numbers.

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