DnD Attack Rolls Explained
Attack rolls sit at the center of almost every combat encounter in Dungeons & Dragons — the moment when the game asks whether an action actually lands. Whether a fighter swings a longsword, a wizard hurls a Fire Bolt, or a rogue tries to sink a dagger into an unsuspecting guard, the attack roll is the mechanical handshake between intention and outcome.
Definition and scope
An attack roll is a d20 roll made to determine whether an attack hits its target. The result — modified by relevant bonuses — is compared against the target's Armor Class (AC). If the modified roll meets or exceeds the AC, the attack hits and the attacker rolls damage. If it falls short, nothing happens except the passing of a moment and, sometimes, a deeply personal silence at the table.
This mechanic appears throughout the core rules published by Wizards of the Coast in the Player's Handbook (5th Edition). It applies to weapon attacks, spell attacks, and certain special abilities. For a broader picture of how combat and other systems fit together, the Key Dimensions and Scopes of DnD overview is a useful reference point.
How it works
The basic formula has three moving parts:
- Roll a d20 — the baseline of randomness that makes every swing genuinely uncertain.
- Add your attack bonus — this is typically the sum of the relevant ability modifier (Strength for most melee attacks, Dexterity for finesse and ranged attacks, the spellcasting ability modifier for spell attacks) plus your proficiency bonus if the attack uses a weapon or spell you are proficient with.
- Compare to AC — if the total equals or exceeds the defender's AC, the attack hits.
Proficiency bonuses in 5th Edition range from +2 at 1st level to +6 at 20th level, meaning a veteran fighter's attack bonus is meaningfully higher than a fresh adventurer's — which is exactly how it should feel.
Two special outcomes break from the standard comparison. A natural 20 (the die itself showing 20, before modifiers) is a critical hit: the attacker rolls all damage dice twice. A natural 1 is an automatic miss, regardless of bonuses — no modifier in the game is large enough to save it. These two results are sometimes called "crits" and "fumbles" respectively, though the rules as written only define the automatic miss, not a mechanical fumble effect. House rules vary widely on the latter.
The How It Works section of this site covers the broader action economy that surrounds attack rolls, including the Attack action, bonus action attacks, and the Extra Attack feature that higher-level fighters and rangers gain.
Common scenarios
Melee weapon attack: A barbarian swings a greataxe. Strength modifier (+4) plus proficiency bonus (+3) equals +7. Against an enemy with AC 15, the player needs a 8 or higher on the d20 — roughly a 65% chance of hitting.
Ranged weapon attack: An archer fires at a target 80 feet away. Longbows have a normal range of 150 feet and a long range of 600 feet, so 80 feet is clean. At long range, disadvantage applies — the player rolls 2d20 and takes the lower result, which substantially shifts the odds against a hit.
Spell attack: A warlock casts Eldritch Blast. Spell attacks use the spellcasting ability modifier (Charisma, in this case) plus proficiency bonus. No spell components or attack actions differ mechanically from a weapon attack roll — the same formula, different flavor.
Advantage and Disadvantage: These conditions modify the d20 roll itself rather than adding a numerical bonus. With advantage, the player rolls 2d20 and takes the higher. With disadvantage, the lower. Importantly, multiple sources of advantage do not stack — a character either has it or does not. Advantage and disadvantage also cancel each other out exactly: one source of each results in a straight roll, even if the character has 3 sources of advantage and 1 of disadvantage.
Questions about edge cases around these scenarios — including unseen attackers, cover, and the Help action — are addressed in the DnD Frequently Asked Questions.
Decision boundaries
The attack roll system creates meaningful tactical decisions at several points.
Ranged vs. melee positioning: Firing into melee (where an adjacent hostile creature threatens the shooter) imposes disadvantage on ranged attack rolls. This creates genuine pressure around positioning — whether to stay back and accept disadvantage or close in and risk opportunity attacks.
The Sharpshooter and Great Weapon Master tradeoff: Both feats (from the Player's Handbook) allow a player to take a −5 penalty to the attack roll in exchange for +10 damage on a hit. This is a high-variance gamble that favors characters who already have high attack bonuses. Against a target with AC 12, a fighter with a +8 attack bonus hits on a 4 or higher; accepting the −5 still hits on a 9 or higher. Against AC 18, the calculus shifts significantly.
Spell attacks vs. saving throws: Not all offensive spells use attack rolls. Fireball, for example, calls for a Dexterity saving throw from targets — not an attack roll from the caster. Spells that use attack rolls (Eldritch Blast, Fire Bolt, Guiding Bolt) can critically hit; spells that call for saving throws cannot. This distinction shapes which spells shine against heavily armored enemies (high AC, often lower Dexterity) versus lightly armored ones.
For players working through how these mechanics interact with character building choices, the How to Get Help for DnD page points to communities and resources where specific scenarios get answered quickly. The full rules overview is also the natural starting point for anyone approaching these systems fresh.