How much holy water is needed to cast Protection from Evil and Good?

Question

In the PHB on page 270 we can read in the desription of Protection from Evil and Good that:

Components: V,S,M(holy water or powdered silver and iron, which the spell consumes)

Since the material components are consumed, they cannot be replaced with a spellcasting focus, as per the PHB (p.203)

If a spell states that a material component is consumed by the spell, the caster must provide this component for each casting of the spell.

This is reinforced by sage advice:

A spellcasting focus can be used in place of a material component only if that component has no cost noted in the spell’s description and if that component isn’t consumed.

The description does not list a cost in gp though. Which brings about the question above. While holy water is created in discrete 25gp "units", powdered silver and iron are not, so we cannot just assume that you need 1 unit of holy water (ie. 25gp worth).

So, is a sprinkle of holy water enough? (Allowing the caster to use 1 unit for multiple castings.)

If one would use silver and iron, how much would they need? 25gp worth? Just "some"?

Answer 1

As with any component that does not specify a specific amount, either by size/weight description, or by cost, the amount is any amount. A pinch, a drop, a dollop, or a house sized mound are all valid amounts that would cause the spell to function. The fact that one possible component listed is sold by the flask according to the equipment list does not change this. In fact, no separate purchase is necessary, as a component pouch contains "all the material components... you need except for those components that have a specified cost," (component pouch description) which this does not. Carry a component pouch, and your needs are satisfied.

Answer 2

Holy water does not necesseraly come in "perfect units of 25 gp".

Protection from Evil is a pretty basic spell. Since no price is specifically listed, only a few drops are required.

Otherwise the material component entry would have been written like this:

Components: V,S,M (25 gp of holy water or of powdered silver and iron, which the spell consumes)

Or like this:

Components: V,S,M (one vial of holy water or powdered silver and iron, which the spell consumes)

Just use common sense.

It would not make any sense to require a full 25 gp vial of holy water, while requiring only a little bit of silver and iron.

And 25 gp of silver and iron, that would weight at minimum a full whopping 5 pounds, making such a common, basic spell, ridiculously costly and impractical.

Use the "spell focus/components pouch can't replace material components" rules only for spells which specifically list a gp cost.