How loud/obvious is a wizard casting a spell?

Question

Some spells have somatic and vocal components, that's well known.

How loud must a wizard talk? How obvious/wide should his gestures be?

Some spells that would be awesome would be fairly limited if you need to shout them (ex: mage hand, range 30ft).

Answer 1

There's no restriction on volume, but gestures are pretty obvious.

The Player Basic Rules p79 says:

Verbal: Most spells require the chanting of mystic words... the particular combination of sounds, with specific pitch and resonance.

Somatic: Spellcasting gestures might include a forceful gesticulation or an intricate set of gestures.

Note that volume is not listed as important. The wizard must speak loudly enough to clearly enunciate her mystic words; a low voice would work, but a whisper might not be clear enough. Gestures are either forceful or intricate, which would be pretty obvious if visible.

A Dexterity check using the Stealth or Sleight of Hand skills is the way to go if you want to speak clearly but quietly or if you want to hide forceful or intricate gestures. If the wizard doesn't care if anyone notices, don't bother with a check; nearby people notice, as appropriate to the story. If the wizard does care, she should make a check with the normal rules.

Answer 2

It is up to the DM, but the casting is noticeable

In 5e nowhere does it define anything specifically defining the volume of spells or how grand gestures have to be. These kinds of details are left entirely up to the DM to decide.

Verbal (V)

Most spells require the chanting of mystic words. [...] the particular combination of sounds, with specific pitch and resonance.

[...]

Somatic (S)

Spellcasting gestures might include a forceful gesticulation or an intricate set of gestures. [...]

This is all the detail we get from the rules. Clearly, gestures must be made and sounds must be produced, but the exact extent of beyond being audible and visible is not solidly layed out.

It is worth noting that the rules do even say that there is a potential range of how obvious the somatic component might be, so it may even depend on the spell.

Jeremy Crawford has shed some light on the intent for verbal components though (in an old unofficial tweet):

The verbal component of a spell must be audible to work. How loud is audible? That's up to the DM.

One thing is sure though: both the verbal and somatic components are definitely noticeable however. We know this because there is at least one class feature, a Sorcerer's Subtle Magic metamagic, whose only purpose is to make them not noticable:

When you cast a spell, you can spend 1 sorcery point to cast it without any somatic or verbal components.

In the end, your DM will have to decide how they want it to work in their world.

Answer 3

It would certainly depend on the spell, but I'd say most of the time he's obvious enough. Though there is no real guidance on this, all of the spell caster art has them being quite vociferous in their casting.

So if you want to make a perception check out of it, DC5 or so.

Now if a character were trying to cast a spell without being seen or heard (something the rules do not currently support), I'd make them make a stealth check prior to attempting the spell. This would effectively be them trying to cast while whispering and making more subtle motions. The DC of the spell would be the passive perception of all creatures around, and particularly bad failures may result in no spell being cast at all.

Answer 4

Components must be as conspicuous as to make spellcasting recognizable - narratively and for balance

I come late to the party, but I thought I could give my 2 cents. If you look at a spell's metadata, you'll find two types of specifications: insight on its workings (school of magic, area and time of effect, ritual casting etc) and requirements (concentration and components).

The manuals explain pretty clearly why a spell the requires concentration is inherently weaker than a hypothetically identical one which doesn't: only one concentration spell can be cast at a time, and attacks and conditions can break it relatively easily, therefore inducing enemies to attack the spellcaster in order to dispel the effects. Concentration limits the enchanter and turn him into a a high priority moving target. Some situations may call for strong spells, but circumstances where concentration is not likely to last may instead encourage less effective solutions that don't need it. You could it's a high risk/high reward mechanic.

Spell components are supposed to bear a similar onus, and render inherently less appealing incantations that need 2 or all 3 of them. Expensive material components are self-evidently costly, but verbal and somatic are often ignored since they offer yet another layer of intricacy and rarely come into play anyway. I've mostly seen reluctance to recur to flashy magic in delicate social situations: exchange of hostages, arrests, audiences with authorities etc, and it makes sense: spells are conspicuous, and even laymen understand that when a guy in the plaza starts to intone a chant while dancing the macarena, they could end up in ashes. Magic is mysterious and therefore dangerous, especially if one doesn't understand its intricacies: I've seen people irl getting paranoid hearing someone in the same room talking in a foreign language, you can imagine that it wouldn't be weird for a bystander to get itchy and change direction or even call the guards at the first sign of spellcasting.

So, what to do when a character invariably tries to cast a spell inconspicuously, either hiding gestures, whispering intonations or weaving them into a seamless dance/speech? Stealth, Deception or Performance checks are a common answer, but I like to add another hurdle: a check to verify if the spell goes off. Whenever the caster contaminates the choreography of a spell for whatever reason -to hide its intentions, it this case- I like to think that it may not work, so what I ask is for a check with spellcasting ability+proficiency bonus; the more seamless, the higher the necessary DC. This way, potent spellcasters can mutter a few words under a cough and a quick movement, while novices trying the same would end up with stares upon them and no magic.

Mechanically speaking, spells are by far the strongest and most versatile asset in the game, therefore their complexity, risks and limitations have an important role in balancing their use against similar alternatives. A rigorous approach on components may hold the party's wizard from resorting to spells as an easy passepartout to every problem -especially if magic attracts some suspicion- and perhaps let other players try less convenient but safer solutions. I can't guarantee on that though.