DnD Damage and Hit Points Rules

Damage and hit points form the mechanical backbone of Dungeons & Dragons combat, translating the narrative of swords, spells, and monsters into a quantified system of attrition and survival. These rules govern how creatures lose and recover vitality, when characters fall unconscious, and how lethal force is calculated across every encounter. Precise understanding of these mechanics is essential for both Dungeon Masters structuring balanced encounters and players making tactical decisions under the core combat framework.

Definition and scope

Hit points (HP) represent a creature's combined physical endurance, will to fight, and luck in avoiding decisive blows — not simply raw biological tissue. The fifth edition rules, published by Wizards of the Coast in the Player's Handbook, define hit points as a pool that begins at maximum at the start of each day (or after a long rest) and is reduced by damage from attacks, spells, traps, and environmental hazards.

Every character's maximum hit point total is determined at character creation and increases with each level gained. At 1st level, a character receives the maximum value of their class's Hit Die plus their Constitution modifier. The Fighter class, for example, uses a d10 Hit Die, while the Wizard uses a d6. At each subsequent level, the player either rolls that Hit Die or takes the fixed average value (half the die's maximum, rounded up — so 6 for a d10, 4 for a d6) and adds their Constitution modifier again.

Damage, conversely, is the mechanism that reduces hit points. Every weapon, spell, and hazard deals a specified dice expression of damage — such as 2d6 for a greatsword or 8d6 for a Fireball spell at 3rd spell slot level. The full scope of damage sources spans weapons, spells, poisons, environmental hazards, and falling.

How it works

When an attack roll succeeds against a target's Armor Class — a process detailed on the attack rolls reference page — the attacker rolls the weapon or spell's damage dice and adds the relevant modifier (typically Strength for melee, Dexterity for ranged, or the spellcasting ability modifier for spells). That total is subtracted from the target's current hit points.

The damage calculation sequence follows this structure:

  1. Determine hit — the attack roll meets or exceeds the target's AC.
  2. Identify damage type — slashing, piercing, bludgeoning, fire, cold, necrotic, radiant, psychic, thunder, lightning, acid, force, or poison.
  3. Roll damage dice — using the weapon or spell's listed dice expression.
  4. Apply modifier — add the relevant ability modifier.
  5. Apply resistance or vulnerability — a resistant creature takes half damage (rounded down); a vulnerable creature takes double damage.
  6. Apply immunity — an immune creature takes 0 damage from that type entirely.
  7. Subtract from current HP — the result reduces the target's hit point total.

Critical hits — scored when the attack roll result is a natural 20 on the d20 — double all damage dice rolled before adding modifiers. A greatsword's critical hit rolls 4d6 instead of 2d6, then adds the Strength modifier once.

Temporary hit points function as a separate buffer that absorbs damage before the main HP pool. They do not stack; a character granted 10 temporary HP who already has 6 retains only 10. Temporary HP expire after a long rest and are not restored by healing.

Common scenarios

Massive damage and instant death: If a single damage instance reduces a character to 0 HP and the remaining damage equals or exceeds the character's maximum HP, the character dies instantly — no death saving throws. A character with a maximum of 12 HP who is at full health and takes 24 damage in a single hit dies outright.

The unconscious state and death saving throws: Reaching 0 HP renders a creature unconscious and triggers the death and dying rules. At 0 HP, player characters make death saving throws at the start of each turn — rolling a d20 with no modifiers. A roll of 10 or higher counts as a success; 1–9 counts as a failure. Three successes stabilize the character; three failures result in death. A natural 1 counts as 2 failures; a natural 20 restores 1 HP immediately.

Healing: The Cure Wounds spell restores 1d8 + the caster's spellcasting modifier in hit points. A short rest allows the expenditure of Hit Dice — rolling the class Hit Die and adding Constitution modifier per die spent. A long rest restores all lost hit points and up to half the character's total Hit Dice. Full rest mechanics are covered under resting rules.

Area damage contrast — single-target vs. multi-target: A Fireball at 3rd spell slot level deals 8d6 fire damage to every creature in a 20-foot radius sphere. Each creature rolls a Dexterity saving throw against the caster's spell save DC; success halves the damage. A single-target attack such as a Scorching Ray beam deals 2d6 fire damage per ray with no saving throw — only an attack roll. The saving throws reference covers DC calculation in full.

Decision boundaries

The rules draw firm distinctions between several adjacent concepts that affect how damage resolves:

Resistance vs. immunity: Resistance halves damage (rounded down); immunity reduces damage to 0. These are not interchangeable. A creature resistant to fire that takes 15 fire damage receives 7 (rounded down). An immune creature receives 0.

Temporary HP vs. healing: Temporary hit points cannot be restored by healing spells; they are a separate pool. The Healing Word spell, for instance, cannot top up temporary HP — it only restores the main pool, and only up to the character's maximum.

Nonlethal damage: An attacker can choose, when dealing a killing blow with a melee attack, to knock the target unconscious rather than kill them. This decision must be made at the moment of the hit, not after rolling damage.

Concentration and damage: When a concentrating spellcaster takes damage, they must succeed on a Constitution saving throw — DC 10 or half the damage taken, whichever is higher — or lose concentration on their active spell.

The how-dnd-works-conceptual-overview page situates these mechanics within the broader action economy and rules structure. The full dndrules.com rules index provides access to all adjacent rule categories referenced throughout this entry.

References

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