D&D Damage Calculator

About This Tool

The D&D Damage Calculator is a free tool for Dungeons & Dragons players and Dungeon Masters who want to quickly calculate expected damage output for any dice combination. Whether you are building a new character, comparing weapon options, or adjudicating combat at the table, this calculator gives you instant access to average damage, minimum and maximum values, and a random roll simulator that shows each individual die result.

How Damage Rolls Work in D&D 5e

In Dungeons & Dragons Fifth Edition, damage is determined by rolling one or more dice and adding a modifier. The dice type depends on the weapon or spell being used. A longsword deals 1d8 slashing damage, a fireball deals 8d6 fire damage, and a greataxe deals 1d12 slashing damage. Your ability modifier (Strength for melee weapons, Dexterity for finesse and ranged weapons) is added to weapon damage rolls. Spell damage typically does not add an ability modifier unless a class feature says otherwise.

Critical Hits and Extra Dice

When you score a critical hit (rolling a natural 20 on your attack roll), you double the number of damage dice before rolling. A longsword that normally deals 1d8+4 instead deals 2d8+4 on a critical hit. Note that only the dice are doubled, not the modifier. Some class features add additional critical hit dice: the Barbarian's Brutal Critical adds one or more extra dice at higher levels, and the Half-Orc's Savage Attacks racial feature adds one additional weapon die on a melee critical hit.

Advantage and Disadvantage on Damage

Standard D&D 5e rules apply advantage and disadvantage only to attack rolls and ability checks, not to damage rolls. However, many homebrew rules and variant systems extend this mechanic to damage for added tactical depth. This calculator supports applying advantage or disadvantage to each individual damage die as a house-rule option. With advantage, each die is rolled twice and the higher result is kept. With disadvantage, the lower result is kept. This can dramatically shift the expected damage output.

Comparing Weapon Choices

One of the most common uses for a damage calculator is comparing weapon options. The classic debate is greatsword (2d6) versus greataxe (1d12). Both average 7 damage before modifiers, but the greatsword is more consistent because rolling two dice creates a bell curve that clusters around the average. The greataxe has higher variance, meaning more extreme highs and lows. For characters who benefit from extra critical hit dice (Barbarians, Half-Orcs), the greataxe pulls ahead because each additional critical die is a d12 rather than a d6.

Multi-Attack and Per-Round Damage

Many martial characters make multiple attacks per round. A 5th-level Fighter with Extra Attack swings twice per round. To estimate per-round damage, calculate the damage for a single hit and multiply by the expected number of hits based on your attack bonus versus the target's Armor Class. A Fighter with +7 to hit against AC 15 needs an 8 or higher on a d20, hitting 65% of the time. Two attacks at 1d8+4 (average 8.5 each) with 65% accuracy yields about 11 expected damage per round. This calculator handles the individual roll; combine results with hit probability for full per-round estimates.

Spell Damage Scaling

Many damage-dealing spells scale with level. Fireball at 3rd level deals 8d6 fire damage (average 28), increasing by 1d6 per slot level above 3rd. Cantrips like Fire Bolt scale with character level, dealing 1d10 at 1st level and up to 4d10 at 17th level. Use this calculator to quickly compare damage at different spell slot levels or to see how your cantrip damage grows as you level up. Remember that spell damage usually benefits from saving throws (half damage on a successful save for area spells) rather than attack rolls.