In the Harry Potter universe it is established that the number seven has magical properties, and is the most powerfully magical number. But what does that mean? What are these 'magical properties' and how do they manifest?

To clarify, I'm not interested in the reasons why seven was chosen as the most magically powerful, but rather what it means for a number to be magically powerful, because beyond cropping up a bunch of times I'm unsure what the innate magical property of the number seven is.

  • Related, borderline dupe: Harry Potter: Why 7?
    – Jenayah
    Commented Dec 17, 2018 at 20:54
  • @Jenayah Yes, I'm aware of that question, but it only establishes that the number seven is magical without an explanation of what that actually means in terms of an in universe effect.
    – Ongo
    Commented Dec 17, 2018 at 20:56
  • Aye, hence why I only linked, not voted to close. Though I'd think the detail of said magical properties could be included in the linked question.
    – Jenayah
    Commented Dec 17, 2018 at 20:58
  • 1
    You should ask the number 6, I hear it's afraid of 7.
    – Misha R
    Commented Nov 10, 2020 at 5:40
  • 1
    Seven deadly sins, seven ways to win, seven holy paths to hell and your trip begins. Seven downward slopes, seven bloody hopes, seven are your burning fires, seven your desires...
    – Bardo
    Commented Nov 10, 2020 at 13:12

3 Answers 3


Numerology is a real-life belief that certain numbers hold more or less magical, divine, or otherwise supernatural power. In Harry Potter it appears to be an established fact, and study of this phenomenon is called Arithmancy and is taught at Hogwarts.

The description of the discovery of the "theorem" of the power of seven from the PS3 game Wonderbook: Book of Spells suggests some sort of hard scientific process is involved.

It was one day, during breakfast, that Wenlock wrote the immensely famous theorem that supported the magical properties of the number seven. She wrote it down on what she thought was the back of an envelope, in the usual invisible ink. That same day, she posted a letter to her cousin, using what she later realised was the envelope in which she had written the theorem.

So why, mathematically, scientifically, is seven more powerful than other numbers (and why is six so afraid of it)? Oddly enough, the precise theoretical underpinnings of the mystical forces driving the universe were left out of the children's video game.

I'm being flip, but the answer for now is... who knows? You may as well ask why thinking happy thoughts and saying Latin words make white animals shoot out of a piece of wood with a bird's feather in it. Magic in the Harry Potter is magical, defying hard explanations. Other than the fact that we know there is such a thing as "magical theory," the books go into little detail about how magic actually works (for the best, in my opinion).

  • Yes but the books do detail the effects of magical properties. Wands have the property of being a conduit for magic, a Patronus has the property of warding off Dementors. All of these things have magical properties that enable a result, even if the mechanics behind those properties aren't known (magical theory being a discipline not greatly explored since it detracts from the main story). I'm not asking why 7 is magical, but since it is how does that magic take effect and actually benefit a witch/wizard who incorporates 7 into their magic (e.g. Voldemort's ideas on splitting his soul).
    – Ongo
    Commented Dec 18, 2018 at 0:43
  • Why is 6 afraid of 7? Because 7 8 9. My return to 4th grade is complete. I'll show myself to the door...
    – FreeMan
    Commented Nov 10, 2020 at 13:20

Within Harry Potter itself I can only think of a single other instance aside from Voldemort's Horcruxes where the number 7 demonstrated a magical effect. In The Half Blood Prince, Harry is using an old potions book with notes in, and by doing so is gaining a reputation as a Potions genius. While making a Draught of Living Death he comes across these note;

According to the book, he had to stir counter-clockwise until the potion turned clear as water. According to the addition the previous owner had made, however, he ought to add a clockwise stir after every seventh counter-clockwise stir. Could the old owner be right twice?

So in this instance the number seven is manifesting as improved potion making techniques. Harry goes on to win the contest Slughorn is staging at this point in the book.

  • 1
    If you're adding a clockwise stir after every seventh counter-clockwise stir, then the clockwise stir is every eighth stir. The clockwise stir is what makes the difference, so this really seems to be an example of the number eight having a magical effect. Commented Dec 18, 2018 at 10:14
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    @AnthonyGrist unless the clockwise stir isn't want is important, it's just the mechanism used to break the counter-clockwise stirs into groups of 7.
    – Jontia
    Commented Dec 18, 2018 at 11:14

Throughout history, many numbers have been considered magical in and of themselves, and the number seven is one of them.

From the Bible, the world was created in 7 days, anyone who dares to kill Cain will suffer vengeance seven times over, Pharaoh dreamed of 7 fat cows followed by and devoured by 7 thin cows (7 bountiful years followed by 7 bad years), and Jacob worked 7 years for Leah and 7 years for Rachel. I'm sure there are more.

In more modern folk belief, the 7th son is supposed to be something special, and the 7th son of a 7th son is miraculous (which is the idea in Orson Scott Card's The Tales of Alvin Maker series).

Other examples are the 7 cardinal virtues and 7 deadly sins, the 7 hells and 7 heavens of Islam, and the Seven Sleepers, and the Seven Sisters (the Pleiades).

It seems likely that J.K. Rowling drew on this tradition in Harry Potter- probably especially the 7th son idea. I don't, however, recall any specific effects of the number 7 mention in Harry Potter - unlike in Terry Pratchett's Discworld books, where the number 8 has numerous powerful effects.

  • I thought of Pratchett while writing this question - his use of 8 is shown to be significant in many aspects of the magic of the Disc. My issue is that the HP universe definitively states 7 to be the most magical but I don't understand how since 7 appears mainly in mundane places (7 Weasley children, 7 floors of Hogwarts, 7 years of school etc.) rather than being magically significant. I'm sure you could find collections of other small numbers in the HP universe that are just due to statistics rather than magical underpinnings (e.g. 4 marauders, 4 houses, 4 Triwizard champions...)
    – Ongo
    Commented Dec 18, 2018 at 16:14
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    Well that's the difference between Pratchett and Rowling. Pratchett did a fantastic job at architecture the foundations and for the most part was quite consistent wiki.lspace.org/mediawiki/Numerology
    – Naib
    Commented Dec 18, 2018 at 16:59
  • This seems more like an answer to the question of why seven is considered magical (scifi.stackexchange.com/q/106582/98028) rather than to this question ("what it means for a number to be magically powerful"), apart from the very last part where you say you don't recall any examples.
    – tardigrade
    Commented Nov 10, 2020 at 6:59

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