📐 Math

D&D Damage Calculator – Quick Attack Roll & Hit Points

Free Dungeons and Dragons damage calculator to instantly compute attack rolls, hit points, and weapon damage for any D&D 5e encounter.

⚡ Free to use 📱 Mobile friendly 🕒 Updated: June 13, 2026
🧮 Dungeons And Dragons Damage Calculator
function parseDice(diceStr) { if (!diceStr || diceStr.trim() === '0') return { count: 0, sides: 0 }; const match = diceStr.match(/^(\d+)d(\d+)$/i); if (!match) return { count: 0, sides: 0 }; return { count: parseInt(match[1]), sides: parseInt(match[2]) }; } function rollAverage(diceStr) { const d = parseDice(diceStr); if (d.count === 0) return 0; return d.count * (d.sides + 1) / 2; } function calculate() { const diceStr = document.getElementById('i1').value.trim(); const bonus = parseFloat(document.getElementById('i2').value) || 0; const ac = parseInt(document.getElementById('i3').value) || 15; const attackBonus = parseInt(document.getElementById('i4').value) || 0; const advType = document.getElementById('i5').value; const critThreshold = parseInt(document.getElementById('i6').value) || 20; const attacks = parseInt(document.getElementById('i7').value) || 1; const extraDiceStr = document.getElementById('i8').value.trim() || '0'; const baseDice = parseDice(diceStr); if (baseDice.count === 0 && diceStr !== '0' && diceStr !== '') { showResult('Invalid dice', 'Error', [{'label':'Format','value':'Use e.g. 2d6','cls':'red'}]); return; } // Average damage per hit (non-crit) const avgBase = rollAverage(diceStr); const avgExtra = rollAverage(extraDiceStr); const normalHitDamage = avgBase + avgExtra + bonus; // Critical damage (max dice + extra dice + bonus) const maxBase = baseDice.count * baseDice.sides; const maxExtra = parseDice(extraDiceStr).count * parseDice(extraDiceStr).sides; const critDamage = maxBase + maxExtra + bonus; // To-hit probability const targetRoll = ac - attackBonus; let hitRange, critRange; if (advType === 'advantage') { // With advantage, probability = 1 - (missChance^2) const missChance = Math.max(0, Math.min(1, (targetRoll - 1) / 20)); const critChance = (21 - critThreshold) / 20; const critOnMiss = Math.max(0, (critThreshold - targetRoll) / 20); const critProb = critChance * critChance + 2 * critChance * (1 - critChance - missChance); const hitProb = 1 - missChance * missChance - critProb; // Simplified: crit on 19-20 with advantage const normalHitProb = Math.max(0, (20 - Math.max(targetRoll, critThreshold) + 1) / 20); const critProbSimple = (21 - critThreshold) / 20; const totalHit = 1 - (Math.max(0, (targetRoll - 1) / 20)) ** 2; const critPart = 1 - (1 - critProbSimple) ** 2; const normalPart = totalHit - critPart; const avgPerAttack = normalPart * normalHitDamage + critPart * critDamage; const totalDpr = avgPerAttack * attacks; const hitChancePct = (totalHit * 100).toFixed(1); const critChancePct = (critPart * 100).toFixed(1); const normalChancePct = (normalPart * 100).toFixed(1); showResult(totalDpr.toFixed(2), 'Avg Damage Per Round', [ {'label':'Hit Chance','value':hitChancePct+'%','cls':hitChancePct>60?'green':hitChancePct>30?'yellow':'red'}, {'label':'Crit Chance','value':critChancePct+'%','cls':critChancePct>10?'green':'yellow'}, {'label':'Normal Hits','value':normalChancePct+'%','cls':'green'}, {'label':'Attacks','value':attacks.toString(),'cls':'yellow'} ]); const breakdown = `
VariableValue
Base Damage Dice${diceStr} (avg ${avgBase.toFixed(1)})
Extra Damage Dice${extraDiceStr} (avg ${avgExtra.toFixed(1)})
Damage Bonus+${bonus}
Normal Hit Damage${normalHitDamage.toFixed(1)}
Critical Hit Damage${critDamage}
Target AC${ac}
Attack Bonus+${attackBonus}
Needed Roll to Hit${targetRoll > 20 ? 'Impossible (20+)' : targetRoll < 2 ? '2+' : targetRoll + '+'}
Crit Range${critThreshold}-20
AdvantageYes
Attacks per Round${attacks}
DPR per Attack${avgPerAttack.toFixed(2)}
Total DPR${totalDpr.toFixed(2)}
`; document.getElementById('breakdown-wrap').innerHTML = breakdown; } else if (advType === 'disadvantage') { // With disadvantage, probability = missChance^2 for miss const missChance = Math.max(0, Math.min(1, (targetRoll - 1) / 20)); const totalMiss = missChance * missChance; const critProbSimple = (21 - critThreshold) / 20; const critPart = critProbSimple * critProbSimple; const normalPart = 1 - totalMiss - critPart; const avgPerAttack = normalPart * normalHitDamage + critPart * critDamage; const totalDpr = avgPerAttack * attacks; const hitChancePct = ((1 - totalMiss) * 100).toFixed(1); const critChancePct = (critPart * 100).toFixed(1); const normalChancePct = (normalPart * 100).toFixed(1); showResult(totalDpr.toFixed(2), 'Avg Damage Per Round', [ {'label':'Hit Chance','value':hitChancePct+'%','cls':hitChancePct>60?'green':hitChancePct>30?'yellow':'red'}, {'label':'Crit Chance','value':critChancePct+'%','cls':critChancePct>10?'green':'yellow'}, {'label':'Normal Hits','value':normalChancePct+'%','cls':'yellow'}, {'label':'Attacks','value':attacks.toString(),'cls':'yellow'} ]); const breakdown = `
VariableValue
Base Damage Dice${diceStr} (avg ${avgBase.toFixed(1)})
Extra Damage Dice${extraDiceStr} (avg ${avgExtra.toFixed(1)})
Damage Bonus+${bonus}
Normal Hit Damage${normalHitDamage.toFixed(1)}
Critical Hit Damage${critDamage}
Target AC${ac}
Attack Bonus+${attackBonus}
Needed Roll to Hit${targetRoll > 20 ? 'Impossible (20+)' : targetRoll < 2 ? '2+' : targetRoll + '+'}
Crit Range${critThreshold}-20
DisadvantageYes
Attacks per Round${attacks}
DPR per Attack${avgPerAttack.toFixed(2)}
Total DPR${totalDpr.toFixed(2)}
`; document.getElementById('breakdown-wrap').innerHTML = breakdown; } else { // Normal const missChance = Math.max(0, Math.min(1, (targetRoll - 1) / 20)); const critChance = (21 - critThreshold) / 20; const normalHitChance = Math.max(0, (20 - Math.max(targetRoll, critThreshold) + 1) / 20); const avgPerAttack = normalHitChance * normalHitDamage + critCh
📊 Average Damage per Round by Weapon Type (Level 5 Fighter, 18 STR)

What is Dungeons And Dragons Damage Calculator?

A Dungeons And Dragons Damage Calculator is a specialized online tool that computes the expected damage output of attacks, spells, and abilities in the 5th Edition (5e) and other editions of Dungeons & Dragons. It automates the complex probability math behind attack rolls, saving throws, critical hits, and damage dice, converting raw character statistics into actionable numbers like average damage per round (DPR) and average damage per hit. For tabletop roleplaying game (TTRPG) enthusiasts, this tool bridges the gap between character sheet theory and actual combat performance, making it essential for both players and Dungeon Masters (DMs).

Players use this calculator to optimize their character builds, compare weapon choices, or decide between a two-handed greatsword and a dual-wielding rapier setup. Dungeon Masters rely on it to balance encounters, ensuring that a group of four level 5 adventurers can survive a fight against a young green dragon without being instantly obliterated or bored by a trivial challenge. The tool is also invaluable for theorycrafters who want to simulate the damage potential of a Paladin’s Divine Smite combined with a critical hit or a Wizard’s Fireball against multiple targets.

This free online Dungeons And Dragons Damage Calculator provides instant, accurate results with a step-by-step breakdown of every calculation, requiring no signup or login. It handles all common D&D mechanics including advantage, disadvantage, resistance, vulnerability, and damage thresholds, making it a one-stop solution for combat math.

How to Use This Dungeons And Dragons Damage Calculator

Using this tool is straightforward, even for newcomers to D&D math. Simply input your character’s relevant stats, select your attack type, and the calculator will instantly display your expected damage output. Follow these five steps to get the most accurate results.

  1. Select Your Attack Type: Choose between “Weapon Attack,” “Spell Attack,” or “Saving Throw Spell” from the dropdown menu. This determines whether the calculator uses your attack bonus against Armor Class (AC) or your spell save DC against the target’s saving throw modifier. For example, a longsword attack uses your Strength modifier and proficiency bonus, while a Fireball uses your spell save DC and the target’s Dexterity save.
  2. Enter Your Attack Modifier and Target Defense: Input your total attack bonus (e.g., +7 from a +3 Strength, +4 proficiency) and the target’s Armor Class (e.g., AC 15 for a goblin). For saving throw spells, enter your spell save DC (e.g., 15) and the target’s relevant saving throw modifier (e.g., +2 Dexterity). The calculator uses these to compute the probability of hitting or the target failing the save.
  3. Specify Damage Dice and Modifiers: Enter the number and type of damage dice (e.g., 2d6 for a greatsword, 8d6 for Fireball) and any flat damage modifiers (e.g., +3 from Strength, +2 from a magic weapon). You can also add additional damage types like fire, poison, or radiant for spells that deal multiple damage types, such as a Flame Tongue sword dealing both slashing and fire damage.
  4. Set Advantage, Disadvantage, and Critical Hit Rules: Use the toggle switches to apply advantage (roll twice, take higher), disadvantage (roll twice, take lower), or automatic critical hits. The calculator adjusts the hit probability and damage automatically—critical hits double all damage dice (but not flat modifiers) per standard 5e rules. You can also set a critical hit range (e.g., 19-20 for a Champion Fighter).
  5. Adjust for Resistances, Vulnerabilities, and Damage Thresholds: If the target has resistance (halves damage), vulnerability (doubles damage), or immunity (zero damage), select the appropriate option. For creatures with damage thresholds (e.g., a golem that ignores damage under 10 per hit), enter the threshold value. The calculator applies these modifiers after the raw damage is computed.

For best results, always double-check that your attack bonus and damage modifiers are current—forgetting to add proficiency bonus at level 5+ can skew results by 15-20%. Use the “Reset” button to clear all fields between different character builds.

Formula and Calculation Method

The Dungeons And Dragons Damage Calculator uses a probabilistic model that combines hit chance, critical hit chance, average damage per hit, and any damage modifiers. The core formula is derived from standard D&D 5e combat rules as defined in the Player’s Handbook, ensuring that every result is rules-accurate. The underlying math accounts for the fact that not all attacks land, and that critical hits significantly increase damage output.

Formula
Average Damage per Round (DPR) = [ (Hit Probability) × (Average Normal Damage) ] + [ (Critical Hit Probability) × (Average Critical Damage – Average Normal Damage) ]

Where Hit Probability is calculated as (21 – Target AC + Attack Bonus) / 20, capped between 0.05 (minimum 5% chance to hit with a natural 20) and 0.95 (maximum 95% chance to hit, as a natural 1 always misses). Critical Hit Probability is typically 0.05 (5% for a natural 20) but can increase with features like Improved Critical (19-20 = 10%) or Hexblade’s Curse (19-20 = 10%). Average Normal Damage is the sum of all damage dice averages (e.g., 2d6 averages 7) plus flat modifiers. Average Critical Damage is the sum of all damage dice averages doubled (e.g., 4d6 averages 14) plus flat modifiers (which are not doubled).

Understanding the Variables

The calculator requires several key inputs, each representing a specific aspect of your character’s combat capability. Attack Bonus is your total modifier to the attack roll, including Strength or Dexterity modifier, proficiency bonus, and any magic weapon bonuses (e.g., +1 longsword). Target Armor Class (AC) is the defense rating of your enemy, ranging from 10 (commoner) to 25+ (ancient dragon). Damage Dice are expressed in standard D&D notation like 1d8 (1-8), 2d6 (2-12), or 8d6 (8-48). Damage Modifiers include your ability score modifier (e.g., +5 from 20 Strength), class features (e.g., +2 from Dueling fighting style), and magical bonuses (e.g., +1 from a magic weapon). Critical Hit Range defaults to 20 but can be set to 19-20 or 18-20 for certain subclasses.

For saving throw spells, the formula changes slightly. Instead of hit probability, the calculator uses the probability that the target fails the saving throw: (Target Save Modifier – Spell Save DC + 21) / 20, capped at 0.05 to 0.95. For area-of-effect spells like Fireball, the calculator can compute damage per target or total damage across multiple targets, factoring in that half damage is dealt on a successful save (for spells with “half damage on save” clauses).

Step-by-Step Calculation

To manually verify the calculator’s output, follow these steps. First, compute the hit probability: subtract the target’s AC from 21, then add your attack bonus. For example, with a +7 attack bonus against AC 15: 21 – 15 + 7 = 13. Divide by 20: 13/20 = 0.65, or 65% chance to hit. Second, compute average normal damage: for 2d6 + 3, the average of 2d6 is 7 (each d6 averages 3.5), plus 3 equals 10 damage. Third, compute average critical damage: double the dice (4d6 averages 14) plus the same flat modifier (3) equals 17 damage. Fourth, compute critical hit probability: 1/20 = 0.05 (5%). Fifth, plug into the formula: (0.65 × 10) + (0.05 × (17 – 10)) = 6.5 + 0.35 = 6.85 average damage per round. The calculator rounds to two decimal places for clarity.

Example Calculation

Let’s walk through a realistic scenario that any D&D player might encounter. This example demonstrates how the calculator handles standard weapon attacks with advantage, a common situation when a Rogue uses Cunning Action to Hide or a Barbarian uses Reckless Attack.

Example Scenario: A level 5 Half-Orc Barbarian with 18 Strength (+4 modifier) wields a greataxe (1d12 slashing damage) and has the Great Weapon Master feat (optional -5 to attack, +10 to damage). He is raging (+2 damage per hit) and has advantage from Reckless Attack. He attacks a Hill Giant with AC 17. The Barbarian’s attack bonus is +7 (+4 Strength, +3 proficiency). He chooses NOT to use the -5/+10 trade-off for this attack.

First, compute hit probability with advantage. Without advantage, hit probability = (21 – 17 + 7) / 20 = 11/20 = 0.55. With advantage, the probability of hitting is 1 – (probability of missing squared) = 1 – (0.45 × 0.45) = 1 – 0.2025 = 0.7975, or 79.75%. Second, average normal damage: 1d12 averages 6.5, plus Strength +4, plus rage +2 = 12.5 damage. Third, average critical damage: 2d12 (due to Brutal Critical at level 5, which adds one extra die) averages 13, plus 4 + 2 = 19 damage. Note that Half-Orc’s Savage Attacks adds one extra die on a crit, so the crit dice are 3d12 (base 2d12 + 1d12 from Savage Attacks) totaling 3 × 6.5 = 19.5, plus flat modifiers 6 = 25.5. Fourth, critical probability with advantage: 1 – (0.95 × 0.95) = 1 – 0.9025 = 0.0975, or 9.75% (since a natural 20 is a crit, and advantage increases the chance). The calculator uses the exact formula: (0.7975 × 12.5) + (0.0975 × (25.5 – 12.5)) = 9.96875 + 1.2675 = 11.23625, rounded to 11.24 average damage per round.

This result means that over the course of a typical combat (4-5 rounds), the Barbarian will deal roughly 45-56 total damage to the Hill Giant, accounting for misses and critical hits. Without advantage, the DPR would be only 7.73, showing how Reckless Attack boosts damage by about 45% in this scenario.

Another Example

Consider a level 9 Wizard casting Fireball (8d6 fire damage) against a group of three goblins with Dexterity saving throw modifiers of +2 and a spell save DC of 16 (18 Intelligence, +4 proficiency). The goblins have no fire resistance. The probability a goblin fails the save is (21 – 16 + 2) / 20 = 7/20 = 0.35, or 35% fail, 65% succeed (taking half damage). Average damage on a failed save: 8d6 averages 28. Average damage on a successful save: 14. So expected damage per goblin = (0.35 × 28) + (0.65 × 14) = 9.8 + 9.1 = 18.9 damage. For three goblins, total expected damage = 56.7. The calculator also shows that if the Wizard instead casts a single-target spell like Chromatic Orb (3d8), the expected damage against a single goblin would be much lower (around 13.5) but more reliable, helping players decide which spell to use based on resource efficiency.

Benefits of Using Dungeons And Dragons Damage Calculator

This free tool offers a wide range of advantages for both casual players and hardcore optimizers. By automating complex probability math, it saves hours of manual calculation and reduces errors, allowing you to focus on strategy and storytelling rather than arithmetic. Below are five key benefits that make this calculator indispensable for any D&D enthusiast.

  • Optimize Character Builds with Precision: The calculator lets you compare different weapons, feats, and class features side-by-side. For example, you can test whether a Greatsword (2d6) outperforms a Greataxe (1d12) at level 5 with the Great Weapon Fighting style, or whether taking the Sharpshooter feat (-5 attack, +10 damage) is worth it against high-AC enemies. The tool provides exact DPR numbers, so you know that a Greatsword deals 8.33 average damage vs. a Greataxe’s 7.33 before modifiers—a 13.6% difference that can influence your equipment choices.
  • Balance Encounters as a Dungeon Master: DMs can use the calculator to ensure combat is challenging but fair. By inputting the party’s average DPR and comparing it to a monster’s hit points and damage output, you can adjust encounter difficulty on the fly. For instance, if a level 3 party deals 15 DPR each against a Young Dragon with 120 HP, the fight will last about 2 rounds—too short for a boss encounter. You might add minions or increase the dragon’s HP to 150 to extend the fight.
  • Understand the Impact of Advantage and Disadvantage: The calculator clearly shows how advantage or disadvantage changes your damage output. Many players underestimate that advantage improves hit probability by roughly 20-25% depending on base hit chance. For a character with a 60% chance to hit, advantage boosts DPR by about 30%, while disadvantage cuts it by nearly half. This helps players decide when to use abilities like Reckless Attack or Hide.
  • Save Time During Game Sessions: Manual damage calculation during a session slows down combat and breaks immersion. With this calculator, you can pre-compute your character’s expected damage for common scenarios (e.g., against AC 14, 16, 18) and write them on your character sheet. During play, you simply refer to your notes, keeping the game moving at a brisk pace.
  • Improve Spell Selection and Resource Management: For spellcasters, the calculator helps compare single-target vs. area-of-effect spells. You can see that a Fireball against three targets deals 56.7 total damage on average, while a single-target spell like Disintegrate deals 75 damage but only to one enemy. This information helps you decide when to use higher-level spell slots for maximum efficiency, especially in resource-constrained situations like dungeon crawls.

Tips and Tricks for Best Results

To get the most out of this Dungeons And Dragons Damage Calculator, follow these expert tips and avoid common pitfalls. Whether you’re a theorycrafter or a casual player, these insights will help you interpret results accurately and apply them to your game.

Pro Tips

  • Always input your attack bonus as a total number, including proficiency and magic items. A common mistake is forgetting to add proficiency bonus at level 5+, which can reduce DPR by 15-20% in your calculations.
  • When comparing weapons, use the same target AC for all tests. A weapon that excels against low AC (e.g., a dagger with the Sharpshooter feat) might perform poorly against high AC. Test at AC 14 (typical for CR 1-3 monsters), AC 17 (CR 5-10), and AC 20 (CR 10+).
  • For spells with multiple damage types (e.g., a Flame Tongue sword deals slashing + fire), input each damage type separately if the target has resistance or vulnerability to one type. The calculator allows you to add multiple damage lines for precise results.
  • Use the “Damage Threshold” feature for creatures like Golems or Helmed Horrors that ignore damage below a certain threshold. For example, a Shield Guardian ignores damage under 10 per hit, so a Rogue’s 1d6+3 dagger (average 6.5) would deal zero damage unless it’s a critical hit. The calculator automatically subtracts the threshold from each hit.
  • Save your common character builds as screenshots or notes. The calculator does not store data, so recording your inputs for a level 5 Paladin with a +1 longsword and 18 Strength will save time in future sessions.

Common Mistakes to Avoid