DnD Damage and Hit Points Rules
Damage and hit points form the mechanical heartbeat of every Dungeons & Dragons combat encounter. Understanding how they interact — from the moment a sword connects to the instant a character drops unconscious — shapes every tactical decision made at the table. This page covers how hit points are calculated, how damage reduces them, and the specific rules that govern edge cases like critical hits, temporary hit points, and death saving throws.
Definition and scope
A hit point is not a measure of flesh and blood. The 5th Edition Player's Handbook describes hit points as representing a combination of physical and mental durability, the will to live, and sheer luck. That framing matters because it explains why a 10th-level fighter can absorb a sword strike that would end a commoner — it is not pure biology, it is narrative resilience made concrete.
Every creature in 5e has a maximum hit point value, derived from Hit Dice, Constitution modifier, and class features. A first-level wizard with a Constitution modifier of +0 starts with 6 hit points (using a d6 Hit Die plus modifier). A first-level barbarian starts with 12 (using a d12). The gap is intentional and significant — and it is the first place new players feel the weight of class choice.
Damage, meanwhile, is the number that subtracts from that total. It arrives through weapon attacks, spells, environmental hazards, and creature abilities. The key dimensions and scopes of DnD page covers how damage types — fire, piercing, psychic, and 10 others — interact with resistances and immunities.
How it works
The core sequence every round of combat follows:
- The attacker makes an attack roll — a d20 plus relevant modifiers — against the target's Armor Class (AC).
Resistance halves incoming damage (rounded down). Vulnerability doubles it. A creature resistant to fire damage that takes 18 fire damage instead takes 9. These modifiers apply after all other arithmetic — the rules specify this order explicitly in the Dungeon Master's Guide.
Critical hits occur when the attack roll shows a natural 20 on the die. The attacker rolls all damage dice twice and adds modifiers once. A rogue's Sneak Attack on a critical hit doubles the Sneak Attack dice as well, not just the weapon dice — this is a common point of confusion at tables, and the rules are clear on the matter.
Temporary hit points operate as a separate buffer, not an extension of the maximum. They do not stack — if a character has 5 temporary hit points and receives another 8, the player takes the higher of the two (8), not 13. Temporary hit points disappear at the end of a long rest and are always consumed before regular hit points.
Common scenarios
Massive damage and instant death: If a single damage instance reduces a character to 0 and the remaining damage equals or exceeds the character's maximum hit points, death is instantaneous — no saving throws. A character with a maximum of 14 hit points, currently at 6, who takes 20 damage has 14 excess damage, which exactly matches their maximum. That character dies outright.
Death saving throws: When a player character drops to 0 hit points (without triggering instant death), they fall unconscious and begin rolling death saves at the start of each of their turns. Three successes stabilize the character. Three failures — accumulated in any order, not necessarily on consecutive turns — mean death. A natural 1 counts as two failures. A natural 20 returns the character to 1 hit point immediately.
Healing at 0: Any healing applied to an unconscious character at 0 hit points restores them to that number of hit points and ends the unconscious condition. A Cure Wounds spell that restores 5 hit points brings the character back to 5 — not to their maximum.
Area-of-effect damage: Spells like Fireball deal damage to every creature in a 20-foot radius sphere. Each creature makes its own saving throw and takes damage independently. The DnD frequently asked questions page addresses whether concentration spells interact with a caster taking damage — which they do, requiring a Constitution saving throw.
Decision boundaries
The rules contain deliberate gray areas that require a Dungeon Master to make a judgment call.
Dropping to 0 on another creature's turn: If a monster takes a legendary action on its turn and that action drops a player to 0, the death save clock starts at the beginning of the player's next turn — not immediately. The sequence of turns matters.
Non-lethal damage: A player character can choose to knock a creature unconscious rather than kill it when reducing that creature to 0 hit points with a melee attack. This is a declared intention at the moment of the kill, not a retroactive choice. Ranged attacks cannot apply this rule under standard 5e rules.
Regeneration and 0 hit points: Some creatures have regeneration — they regain a set number of hit points at the start of their turn. Regeneration does not function while at 0 hit points. A troll at 0 does not regenerate until it regains at least 1 hit point through another means.
For questions about how these rules intersect with specific class features, spells, or monster stat blocks, the how to get help for DnD page outlines the most reliable official and community resources — because even well-run tables encounter a rule that turns out to be more layered than it first appeared.