DnD Combat Rules: A Complete Reference

Dungeons & Dragons combat operates through a structured turn-based framework codified in the fifth edition Player's Handbook and Dungeon Master's Guide, published by Wizards of the Coast. The combat system governs how characters, monsters, and environmental forces interact during violent confrontations — determining who acts, when they act, what actions they may take, and how outcomes are resolved through dice mechanics. This reference covers the full structural architecture of D&D 5e combat, from initiative and action economy through to death saves and encounter termination, serving as a lookup resource for players, Dungeon Masters, and organized play participants.

• Definition and Scope
• Core Mechanics or Structure
• Causal Relationships or Drivers
• Classification Boundaries
• Tradeoffs and Tensions
• Common Misconceptions
• Combat Round Sequence Checklist
• Reference Table: Action Types and Interaction Summary

Definition and Scope

D&D 5e combat is the formalized conflict resolution system used whenever narrative outcomes cannot or should not be left to roleplay alone — specifically when creatures attempt to harm, incapacitate, or kill each other. The Player's Handbook (Wizards of the Coast, 2014, Chapter 9) defines combat as taking place in a series of rounds, each representing approximately 6 seconds of in-game time, and turns, during which each individual participant acts.

The scope of the combat rules encompasses six primary domains:

1. Initiative — determining the order in which all participants act
2. Action economy — what each participant may do on their turn
3. Attack resolution — the dice mechanics that determine whether an attack hits and how much damage it deals
4. Condition tracking — status effects that modify creature capabilities
5. Hit points and death — the resource representing survivability and its depletion
6. Encounter termination — the conditions under which combat ends

Combat rules in 5e apply across three official rule sources: the Player's Handbook, the Dungeon Master's Guide, and the free D&D Basic Rules (Wizards of the Coast / D&D Beyond). The Basic Rules, available without cost, contain the core combat framework sufficient to run most encounters. The broader context of how combat fits within D&D's three pillars — combat, exploration, and social interaction — is covered in How DnD Works: Conceptual Overview.

Core Mechanics or Structure

Initiative and Turn Order

At the start of combat, every participant rolls a d20 and adds their Dexterity modifier — this is the initiative roll. The Dungeon Master ranks all participants from highest to lowest; this ranking, called initiative order, persists for the entire encounter unless a rule or ability explicitly changes it. Ties between player characters and monsters are typically broken by Dexterity score; ties between two player characters are resolved by mutual agreement or a reroll.

The Round and Turn Structure

Each round, every participant takes one turn in initiative order. A turn consists of:

• Movement — up to the creature's speed in feet (typically 30 ft. for humans)
• 1 Action
• 1 Bonus Action (only if a feature grants one)
• 1 Free Object Interaction
• 1 Reaction (usable once per round, potentially outside own turn)

Movement can be broken up before and after actions. The distinction between actions, bonus actions, and reactions is the foundation of D&D 5e's action economy — detailed further in DnD Action Types Explained.

Attack Rolls and Damage

An attack roll determines whether a strike hits. The roll is: d20 + ability modifier + proficiency bonus (if proficient) versus the target's Armor Class (AC). A result meeting or exceeding the AC is a hit. On a hit, the attacker rolls damage dice determined by the weapon or spell, adds the relevant modifier, and subtracts that total from the target's hit points. A natural 20 on the d20 is a critical hit, doubling the number of damage dice rolled. Full mechanics for attack resolution are catalogued at DnD Attack Rolls Explained, and hit point rules are covered at DnD Damage and Hit Points Rules.

Saving Throws

Many spells, traps, and environmental hazards require a saving throw rather than an attack roll. The target rolls d20 + the relevant ability modifier (+ proficiency if proficient) against a Difficulty Class (DC) set by the source. Failing the save typically triggers the full effect; succeeding often reduces or negates it. The six saving throw types correspond to the six ability scores. The DnD Saving Throws Rules page covers these in full.

Causal Relationships or Drivers

The combat system's mechanics create predictable causal chains:

Higher Dexterity → Earlier Initiative → More Actions Before Threats Act. A character with a +5 Dexterity modifier statistically acts before a creature with a +0 modifier in approximately 75% of rounds (assuming standard d20 variance).

Higher AC → Fewer Hits Landed. Each point of AC reduces the probability of a hit by 5% (one face of the d20). A creature with AC 18 is hit by a +5 attack roll on a roll of 13 or higher — a 40% hit rate — versus AC 12, where hits land on a 7 or higher, a 70% hit rate.

Concentration Dependency → Single-Point Failure for Multi-Effect Spells. The DnD Concentration Rules create a direct causal link between taking damage and losing ongoing spell effects: a caster who takes damage must succeed on a Constitution saving throw (DC 10 or half the damage taken, whichever is higher) or lose concentration. This makes casters natural high-value targets.

Action Economy Advantage → Exponential Combat Power. Encounter balance mathematics, as outlined in the DnD Encounter Building Rules, show that four characters acting against one creature create overwhelming action advantage — even if the single creature has equivalent total hit points and damage output.

Classification Boundaries

Surprise

A creature is surprised if it fails to detect an ambush before combat begins. Surprised creatures cannot move or take actions on the first round of combat and cannot take reactions until that turn ends. Surprise requires either a Stealth check opposed by Passive Perception or a Dungeon Master ruling on narrative circumstances.

Types of Attack Actions

• Melee attacks — require the target to be within the weapon's reach (5 ft. for most weapons, 10 ft. for reach weapons)
• Ranged attacks — specify a short range and a long range in feet; attacking at long range imposes disadvantage
• Spell attacks — function identically to weapon attacks mechanically but use the caster's spell attack modifier (spellcasting ability modifier + proficiency bonus)

Conditions

The combat rules define 15 named conditions in the Player's Handbook — Blinded, Charmed, Deafened, Exhausted, Frightened, Grappled, Incapacitated, Invisible, Paralyzed, Petrified, Poisoned, Prone, Restrained, Stunned, and Unconscious — each with specific mechanical effects. A full lookup is available at DnD Conditions Reference.

Cover

The rules classify cover into 3 degrees: half cover (+2 AC and Dexterity saves), three-quarters cover (+5 AC and Dexterity saves), and total cover (cannot be targeted directly). The full framework is at DnD Cover Rules.

Tradeoffs and Tensions

Bounded Accuracy vs. Flat Power Scaling. Fifth edition deliberately caps attack bonuses and ACs within a narrow band — most attack bonuses range from +2 to +11 at level 20, and most creature ACs fall between 10 and 22. This design, called bounded accuracy by Wizards of the Coast, keeps low-level monsters relevant at high levels but creates tension with player expectations of exponential power growth common to other RPG systems.

Reaction Economy. Opportunity attacks (DnD Opportunity Attacks Rules), Shield spells, Counterspells, and class features all compete for the single reaction slot per round. Characters with multiple reaction-triggering features must choose, and missing a reaction window has no recovery mechanism until the following round.

Movement Granularity. The grid-based 5-foot-square movement system used in most combat conflicts with the theater-of-the-mind approach endorsed in the Dungeon Master's Guide. Grid play rewards precise positioning and enables flanking rules (DnD Flanking Rules); theater-of-the-mind play moves faster but introduces adjudication disputes.

Healing Economy. Healing spells in 5e return relatively small hit point totals compared to the damage output at mid and high levels. A 5th-level Cure Wounds spell averages 21 hit points restored, while a 5th-level Fireball averages 28 damage against a single target — making in-combat healing mathematically less efficient than eliminating threats. This tension drives party composition debates.

Common Misconceptions

Misconception: Dropping to 0 HP means instant death.
Correction: Player characters reduced to 0 hit points fall unconscious and begin making death saving throws — not a death check against a fixed DC, but a d20 roll with no modifiers where 10 or higher is a success. Three successes before three failures means the character stabilizes; three failures means death. Full mechanics are at DnD Death and Dying Rules, with resurrection rules at DnD Resurrection Rules. The D&D Beyond Rules Glossary — Death Saving Throw is the authoritative free-to-access source.

Misconception: Bonus actions can be used freely on any turn.
Correction: A bonus action can only be taken if a specific class feature, spell, or rule explicitly grants a bonus action. The rules text in the Player's Handbook (p. 189) states: "You can take a bonus action only when a special ability, spell, or other feature of the game states that you can do something as a bonus action." No bonus action exists by default.

Misconception: Diagonal movement costs the same as orthogonal movement on a grid.
Correction: Under the standard rules, every 5-foot square of diagonal movement costs 5 feet of speed — the same as straight movement. The Dungeon Master's Guide presents an optional rule where every second diagonal costs 10 feet (mimicking real-world geometry), but this is explicitly variant, not default.

Misconception: Grappling and shoving are attack actions separate from the Attack action.
Correction: Both grappling (DnD Grappling Rules) and shoving are special melee attacks made as part of the Attack action — they replace one of the attacks when a character has the Extra Attack feature. They use Athletics checks opposed by Athletics or Acrobatics, not attack rolls.

Misconception: Stealth requires a new roll every round.
Correction: A creature that successfully hides (DnD Stealth and Hiding Rules) retains that condition until it does something to reveal itself (attacking, casting a non-subtle spell, or moving into a visible position). A new check is only required if the circumstances demand adjudication of a new detection opportunity.

Combat Round Sequence Checklist

The following sequence reflects the standard operational order for resolving a D&D 5e combat encounter per the Player's Handbook Chapter 9:

1. Establish surprise — Dungeon Master determines whether any creatures are surprised based on Stealth vs. Passive Perception comparisons
2. Roll initiative — all participants roll d20 + Dexterity modifier; Dungeon Master records results in descending order
3. Begin Round 1 — proceed through initiative order; surprised creatures skip their first turn
4. Execute turns in order — for each creature's turn:
   a. Declare movement (may be split around action)
   b. Declare action (Attack, Cast a Spell, Dash, Disengage, Dodge, Help, Hide, Ready, Search, Use Object)
   c. Declare bonus action (only if a specific rule grants one)
   d. Use free object interaction (draw/sheathe weapon, open door, etc.)
5. Resolve reactions — between any two turns, reactions (opportunity attacks, Shield spell, etc.) may trigger based on applicable conditions
6. Track condition changes — apply or remove conditions (Prone, Grappled, Poisoned, etc.) as effects resolve each turn
7. Check for 0 HP — any creature reduced to 0 HP falls unconscious; player characters begin death saving throw protocol
8. Advance to next turn — repeat until all participants in the round have acted
9. Begin new round — new round starts at the top of initiative order; all per-round resources (reactions, some spell effects) reset
10. Determine encounter end — combat ends when all members of one side are dead, incapacitated, have fled, or have surrendered

Reference Table: Action Types and Interaction Summary

For a complete breakdown of each action type's mechanics and edge cases, see DnD Action Types Explained. Movement rules and positioning interactions are documented separately at DnD Movement and Positioning Rules.

The full D&D 5e combat framework is one component of the broader rules system catalogued at DnD Rules — which also covers spellcasting, equipment, exploration, and social interaction pillars. The DnD Core Rulebooks Explained page identifies which official publications contain binding rule text for organized play and home table use.

References

• D&D Basic Rules — Wizards of the Coast / D&D Beyond (Free Official Reference)
• D&D Beyond Rules Glossary — Death Saving Throw (Official Digital Reference)
• Dungeon Master's Guide — Wizards of the Coast (Variant and Optional Rules)
• D&D Adventurers League — Organized Play Documentation (Wizards of the Coast)
• Player's Handbook — Wizards of the Coast (Chapter 9: Combat)