Damage and Hit Points Rules

Hit points and damage sit at the mechanical heart of every D&D encounter — they determine whether a character survives a dragon's breath, whether a villain falls before the party can stop them, and whether that one unlucky goblin with 4 hit points becomes a footnote or a footnote with a story. These rules govern how combat resolves across every edition of Dungeons & Dragons, with the 5th Edition rules (Player's Handbook, 2014, Chapter 9) serving as the primary reference point here. Getting them wrong doesn't just confuse players — it restructures the entire risk economy of the game.

Definition and scope

A hit point is an abstraction. The Player's Handbook describes it as representing a combination of physical and mental durability, the will to live, and luck. A fighter with 45 hit points who takes a 10-point sword strike hasn't necessarily been cut open — they may have deflected it awkwardly, expended stamina avoiding the worst of it, or simply absorbed it. The number 10 represents narrative consequence compressed into arithmetic.

Damage, correspondingly, is the reduction of those hit points. It comes in 13 distinct types under 5th Edition rules: acid, bludgeoning, cold, fire, force, lightning, necrotic, piercing, poison, psychic, radiant, slashing, and thunder. The distinction matters because resistances, immunities, and vulnerabilities operate per damage type — a fire elemental immune to fire damage cares very much that a spell deals fire rather than force.

Hit points have a hard floor of 0. Damage never pushes a character to a negative number mechanically; the floor is 0, and what happens at 0 is its own separate system.

How it works

When a successful attack or effect deals damage, the sequence follows a consistent structure:

1. Roll the damage dice specified by the weapon, spell, or effect — a longsword deals 1d8 slashing (or 1d10 when wielded with two hands), a fireball deals 8d6 fire.
2. Add relevant modifiers — a melee attack adds the attacker's Strength modifier; a spell attack adds the relevant spellcasting modifier where specified.
3. Apply resistance or vulnerability — resistance halves the damage (rounded down); vulnerability doubles it. These do not stack: multiple sources of resistance still only halve once.
4. Subtract from current hit points — the result reduces the target's hit points by exactly that amount.

Critical hits, which occur on a natural 20 attack roll, double the number of damage dice rolled (not the total). A longsword's critical hit rolls 2d8 rather than 1d8, then adds the normal modifier once. This distinction — double dice, not double total — is one of the most frequently misread rules at the table.

Temporary hit points work as a separate buffer. They absorb incoming damage first but don't stack with other temporary hit points; a character takes the highest value available, not a sum. They also don't restore actual hit points — losing all temporary hit points leaves the character at whatever real hit points they had before the buffer was applied.

Common scenarios

Falling to 0 hit points triggers the unconscious condition and begins death saving throws — three successes stabilize, three failures mean death. Massive damage (damage that reduces hit points to 0 with enough excess to also equal the character's maximum hit points in a single strike) causes instant death. A character with 8 maximum hit points at 0 hit points dies instantly from a hit dealing 8 or more excess damage.

Healing restores hit points up to the maximum — no overshooting. A short rest allows spending Hit Dice (a pool of dice equal to character level, sized by class — d12 for barbarians, d6 for wizards) to recover hit points. A long rest restores all hit points.

Area effects like the fireball spell require a Dexterity saving throw. On a failed save, the target takes full damage; on a success, half damage. Unlike attack rolls, saving throw effects still deal damage on a success — the target just lands behind cover fast enough to avoid the worst.

Concentration damage is an indirect consequence: whenever a concentrating caster takes damage, they must make a Constitution saving throw (DC 10 or half the damage taken, whichever is higher) or lose the spell. A 2-point hit technically demands a DC 10 check; a 40-point hit demands DC 20.

Decision boundaries

Several judgment calls sit in rules-gray territory, and a Dungeon Master resolves them at the table:

Nonlethal damage is cleanly defined for melee attacks — a character can choose to knock a target unconscious at 0 hit points rather than kill them. Ranged attacks and spells do not have this option by default under 5th Edition rules.

Damage type versus effect creates occasional friction. A spell that deals cold damage as a rider on a grapple is still cold damage for resistance purposes. Physical descriptors don't change type unless the rules explicitly say so.

Resistance order of operations matters in edge cases. If a creature has vulnerability to fire and a character has resistance to all damage, the Player's Handbook specifies that resistance and vulnerability cancel — the creature takes normal damage from the fire attack. The FAQ and errata documents from Wizards of the Coast clarify several such stacking interactions in print.

Temporary hit points during transformation (a druid's Wild Shape, for instance) remain their own pool. The druid's real hit points are preserved separately, unchanged, while the beast form absorbs its own damage — another case where the boundary between mechanical pools determines outcomes that feel narratively significant, which is really what these rules are doing all along.