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Harry Potter Wiki
"If being good at Divination means I have to pretend to see death omens in a lump of tea leaves, I'm not sure I'll be studying it much longer! That lesson was absolute rubbish compared with my Arithmancy class!"
— Hermione Granger's opinion of Arithmancy[src]

Arithmancy was a magical discipline that studied the magical properties of numbers, including predicting the future with numbers and numerology.[1] Those who studied and practised Arithmancy were called Arithmancers.

Arithmancy was an elective subject offered from the third year on at Hogwarts School of Witchcraft and Wizardry, the homework assignments of which included writing essays that required the consultation and/or composition of complex numerical charts.[2]


While the class offered as an elective to Hogwarts students from their third year and up appeared to be narrowly focused on predicting the future using numbers,[3] it would seem that in a broader sense, arithmancy occupies to wizards the same role as mathematics does in the Muggle world: The famous thirteenth-century Arithmancer Bridget Wenlock, for example, would write her calculations, including the one that established the magical properties of the number seven,[4] in the form of theorems, which in Muggle terms refer to a proposition or statement that is demonstrated in geometry, showing that mathematics plays at least a part in arithmetical work. Curse-Breakers was also known to be required a passing grade on their O.W.L. exam in the subject, with the reason cited being that banking and transactions were part of their job,[5] and when Cerberus Langarm confiscated the accounts ledger from Slug & Jiggers Apothecary in Diagon Alley, a "really, really long book of boring financial figures", as evidence in an ongoing investigation and delegated the task of going through it to Mathilda Grimblehawk and partner, they in turn passed it along to Sage Bragnam, as he had studied arithmancy.[6]


Numerology and Grammatica,[7] a third year textbook at Hogwarts.

New Theory of Numerology, which Harry Potter gave to Hermione Granger for Christmas in 1995, due to her love and passion for this academic subject.[8]

Notable Arithmancers

Wizard(s) Notes
Bridget Wenlock The archetypal example; she was a celebrated witch who first discovered the magical properties of the number seven in the 13th century.[9]
Septima Vector Taught Arithmancy and Advanced Arithmancy Studies at Hogwarts School of Witchcraft and Wizardry for at least six years (possibly more).
Hermione Granger Famous high-ranking official in the Department of Magical Law Enforcement, who strongly contributed to Voldemort's downfall as she accompanied Harry Potter in the hunt for Horcruxes; translated the Tales of Beedle the Bard into English from Runic.
Ben Copper Achieved an O.W.L. in this subject at Hogwarts.[10]
Percy Weasley Achieved an O.W.L. in this subject at Hogwarts.[10]
William Weasley Achieved an O.W.L. in this subject and worked as a Curse-Breaker for Gringotts Wizarding Bank.[10]
Curse-Breakers An O.W.L. in Arithmancy is required to take the job.[5]

Arithmantic texts


Arithmancer and Arithmancy come from the Greek αριθμός (arithmos), meaning "number", and μαντεία (manteia), meaning "divination". Hence "Arithmancy" literally means "number divination", which is fitting.

Behind the scenes

  • In the real world, the term "Arithmancy" refers to a supposed form of divination based on assigning numerical values to words or phrases; the term "Numerology", referred to in canon as a branch of Arithmancy, refers to any of a number of different beliefs in a divine or mystical relationship between a number and coinciding events.
  • In film adaptation Harry Potter and the Prisoner of Azkaban, Hermione seems to choose Ancient Runes, not Arithmancy, as her favourite subject, comparing its superiority over Divination.
  • In Harry Potter and the Prisoner of Azkaban, Hermione expressed open contempt for the subject of Divination, which she detested because it seemed to be "a lot of guesswork." On the other hand, she also also proclaimed that Arithmancy (in which numerology, a term that in reality refers to any belief in the divine or mystical relationship between a number and one or more coinciding events, is prominent) is her favourite subject. While this may seem contradictory at first, a likely explanation is that Arithmancy applies a more rigorous and mathematical approach to predicting the future, which the scientifically-inclined Hermione would respond well to.
  • If so, the field of Arithmancy might serve as a foil to the wooliness of Divination by basing its predictions on that which is already known. If the inclusion of numerology is any indication, and on the assumption that everything that exist have some numerological value associated with it, an arithmancer can presumably predict the likely behaviour of the world around them by using arithmetical laws to combine those values and interpret the meaning of the results. If so, Arithmancy might, at least in part, deal with the development of predictive models for estimating the probability of a given event taking place.
  • In view of the above, it is easy to see how this would be of value to curse-breakers, as it would allow them to evaluate the potential success of a curse-breaking strategy without having to actually do it, simply by taking the numerology of a counter-curse that they want to use, and the numerology of the curse they want to counter, and use arithmetical laws to analyse how the two interact to and thus greatly minimise the risk of failure and/or injury.
  • In Harry Potter: Hogwarts Mystery, Murphy McNully have been known to on accurately predict the outcome of certain events by calculating the probability of them taking place, be it the estimated chance of success of an attempted Quidditch strategy, or the behaviour of his fellow students. As the wizarding equivalent to mathematics, and given its predictive capabilities, Murphy McNully presumably uses arithmancy in order to calculate probabilities.


Notes and references

External links

Professors: Septima Vector
Known Arithmancers: Sage Bragnam · Lukas Karuzos · Chiara Lobosca's father · Bridget Wenlock
Textbooks: Numerology and Grammatica · New Theory of Numerology
Arithmancy at Hogwarts: Arithmancy (class) · Classroom 7A · Advanced Arithmancy Studies