Often in fantasies involving magic casting spells requires a certain physical or mental toll on the caster. I don't recall any mention of spells being physically or mentally taxing in the Harry Potter universe.

Does this mean they can cast an unlimited number of spells in a given day without any negative effect to themselves?

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    I have a strong feeling there was at least 1 example of that in the book, but drawing a blank. @Slytherincess? Commented Jan 3, 2012 at 21:55
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    I patiently await @Slytherincess' response, which will probably have a reference to Rowling's personal journal. Commented Jan 3, 2012 at 21:56
  • ROFL. Nyah, it's in my brain so must be one of the 7+3 books. Commented Jan 3, 2012 at 22:03

3 Answers 3


There is definitely a canon example of spell casting exhausting the caster.

In Goblet of Fire Harry is exhausted after practicing the summoning charm a zillion times (Accio) in anticipation of the First Task.

There are other examples where some spell-specific resource limits particular spells:

  • the obvious is the creation of the Horcrux which, after a homicide, requires then the splitting off of part of the soul.

  • The casting of the Patronus Charm is contingent upon a witch or wizard being able to conjure up happy memories; several times throughout canon, Harry is unable to muster the positive energy required to produce a full corporeal Patronus. When Harry was learning the Patronus Charm in Prisoner of Azkaban, he was both mentally and physically exhausted by the experience.

  • Legilimens is another spell that is completely mentally exhausting, for both the caster and the recipient of the spell. It involves such mind concentration that of course it would be draining. As well, depending on what the Legilimens sees inside his/her target's head, it could be emotionally overwhelming to boot.

  • Learning Apparition is physically taxing and there's the risk of Splinching. When Ron Splinched in Deathly Hallows, he was quite debilitated.

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    Thanks for taking a stab at it -- you're always there with a good and solid answer for all things HP.
    – Tango
    Commented Jan 4, 2012 at 21:10
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    +1 for thoroughness, but some of these things (like "needing to mean it") I would consider prerequisites, not costs. "Needing to mean it" doesn't take anything out of you, doesn't physically or mentally drain you or such, so isn't really a "cost" -- it's simply necessary for the spell.
    – Joe White
    Commented Jan 17, 2012 at 12:57
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    @JoeWhite - I get what you're saying. I would counter with the idea that for certain spells, one has to confront one's own morality, which can be really hard emotionally. If one were to successfully cast Cruciatus or Avada Kedavra, for example, what does that say about you as a person? Just food for thought. For example, I can imagine Harry, from what we know of his characterization, would be deeply affected by purposefully killing someone -- it might take quite an emotional toll. Yes, it's a prerequisite for casting the curse in question, but it does not come without ramification. :) Commented Jan 17, 2012 at 14:20
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    @Slytherincess - Upon re-reading this answer, most of your examples don't really answer the question at all (they refer to either results of the spell - typically on the target - or specific requirements on the caster, mosly ones that are not "exaustible" such as hate/happiness). As such, I will edit the answer and delete all the mismatched examples, and leave 1 that is 100% correct and on-target (Accio exaustion). Please feel free to roll back if you disagree Commented Apr 16, 2014 at 12:22
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    Harry was definitely very exhausted after his sessions with Lupin. Wasn't Harry's exhaustion due to the (pseudo)Dementor's presence, rather than casting the Patronus? Even on the train, Harry fainted because of the Dementors. In Ootp, the DA perform Patronus charms, but there isn't a sign of exhaustion, is there? My point is that casting the Patronus may not be the reason for the exertion, but the presence of Dementors is. I'm not sure though, I haven't read book 3 in a while :P Commented May 1, 2014 at 17:36

In the 4th book and 4th movie, Mad Eye Moody

Or Barty Crouch disguised

taught the children the three Unforgivable Curses. He mentioned that they all take serious willpower to want to cause harm to another person as well as severe concentration to cast them successfully. He mentioned that the children probably couldn't cause more than a nosebleed if they tried to use Avada Kedavra on him.

From Goblet of Fire:

"Avada Kedavra's a curse that needs a powerful bit of magic behind it - you could all get your wands out now and point them at me and say the words, and I doubt I'd get so much as a nose bleed..."

From Order of the Pheonix:

"Never used an Unforgivable Curse before, have you boy?" [Bellatrix] yelled..."You need to mean them Potter! You need to really want to cause pain - to enjoy it - righteous anger won't hurt me for long..."

So the costs are concentration, control of magic itself, and a will to want to cast the spells. Some of these probably don't "cost" much like lumos or alohomora, but the "price" of others like the Unforgivable Curses would be considerable magic ability and emotional stress from casting them.

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    I wouldn't consider concentration, control or emotional stress to be cost -- I doubt V incurs much emotional stress when using a U Curse.
    – jmoreno
    Commented Jan 4, 2012 at 2:39
  • His soul was split 6 times cause of some of the spells he cast... that seems pretty stressful lol Commented Jan 4, 2012 at 7:05
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    Funny, but as that was the purpose of the spells, I don't think it qualifies as a cost...
    – jmoreno
    Commented Jan 4, 2012 at 8:40
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    Well, consider playing some game that requires a high level of concentration. Chess, or Go, or some video game. Such activities would drain you mentally until you "just can't think anymore", and often such weariness is also felt physically. I would posit that casting a number of advanced spells requiring high concentration in a short time would be similarly draining. There are also spells that seem to have a willpower component; not only do you have to be focused, you have to want it to work, especially if something like a counterspell is working against you.
    – KeithS
    Commented Jan 6, 2012 at 18:25
  • @jmoreno emotional stress is absolutely cost - the brain uses things to cope with that stress, possibly faster than they replenish, and depending on the stress, the body and brain will physically exert themselves to get into and maintain in a state of readiness for action. (Concentration and control, as the prior comment points out, is also a very real mental cost - brain activity and conscious steering of thoughts isn't free.) But you're right that costs like emotional stress are often less inherent to a spell and more about how the caster mentally relates to their use and experience of it.
    – mtraceur
    Commented Jan 22, 2023 at 19:55

Yes, it means by and large, there is no limit on the ability of magic users in the Potterverse, save their ability to maintain their concentration and focus. Counter-spells and counter hexes make targeting other magic-users more difficult, but not impossible. Spells such as Protego (Order of the Phoenix) are used to prevent spells from taking effect, but are considered difficult to learn. (Half Blood Prince)

As long as a spell user has a wand, they are quite capable of performing and manipulating their environment based on their magical training and practical skill with magic. The greater natural talent, magical training and practical skill, the more effective they appear to be with magic and the more effortless they appear to be able to use said magic.

It does not mean there is no cost to the use of magic. Harry's first attempts to use the Patronus Charm to repel the boggart in the classroom with Professor Lupin (Prisoner of Azkaban) was less than successful and later only when it was backed with intense emotion was he able to create it effectively.

Rowling's writings do not seem to indicate significant stress on the part of anyone using magic except for Ron Weasley whose magical aptitude was always questionable in the early days of his education.

In the Harry Potter Universe, magic appears to function as a technology. Humans create technology in order to do work. In the Potterverse, wizards use magic to perform feats such as moving materials or themselves (Apparate or an Animagus' transformation), open doors (Alohomora), altering the composition of matter (Episkey), or altering the capabilities of people using potions (waterbreathing).

As long as the users were working with already known spells they possessed familiarity with, there seemed to be little if any physical fatigue associated with using that magic. In the early stages of magical training, there may be some fatigue until the spell becomes familiar to use.

I suspect part of the reason there is little fatigue is because of their use of wands and other foci in their spell-casting. The focus directs and supports the use of the energy of their magic, the same way a gun directs and releases the energy of a bullet from a gun.

In the same way, you could throw a rock to hit and harm an opponent, it is likely wizards could throw spells in a without a wand to attempt to disable an opponent, but the wand helps focus the magic faster, better, easier and far more effectively. I also suspect the more powerful the spell, or more powerful the effect, the greater the effort and greater the toll it takes on the spell-caster.

This explains why students might even knowing the same spell as their professors lacking the ability to defeat their far more powerful professors in direct confrontation, partially due to the students lacking the focus and concentration to effectively overcome their professors experience manipulating and controlling magical energies.

Many of the magical disciplines, such as potion-making take the effort associated with magic and places it within a potion to be released only upon consumption. So it might take you days to create a complex potion (taxing your strength and creativity until it is done) but it will sit ready once created for immediate use.

Magic acts for all intents and purposes as a means of controlling work, power and effort until such time as needed in the same manner as machines might do for the Muggles who are not part of their magical community.

The Potterverse's approach to magic use is very different from other spell using stories in which wizards or magic-users experience fatigue from their use of magic. But whether there is fatigue or not varies widely from series to series. The convention for wizards possessing limits in literature may come from their long association with role-playing games which put limits on the power of wizards such as mana use or spell use limitations to control the otherwise awesome power wizards have in that medium.

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    This really needs some quotes from the Harry Potter series, otherwise it's pure speculation.
    – thedaian
    Commented Jan 3, 2012 at 22:38
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    I have to agree with @thedaian. It feels as if there is a lot of extra (and unnecessary) explanation here to obscure the fact that there isn't a clear answer. Any chance of editing it to provide support and to make it more succinct?
    – Tango
    Commented Jan 4, 2012 at 7:04
  • I disagree with the comments about the "Feist's Magician Series" I recall then when Pug is looking for the Eldar, there are clear indications that he can't just keep teleporting himself as it takes too much energy.
    – AidanO
    Commented Jan 4, 2012 at 14:36
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    @ThaddeusHowze Apparate is the teleportation spell used throughout the Harry Potter universe. Commented Jan 4, 2012 at 18:06
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    @ThaddeusHowze . . . Wut? stares at your answer Commented Jan 4, 2012 at 18:47

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