How To Calculate Ac Dnd

D&D 5e Armor Class (AC) Calculator

Calculate your character’s Armor Class with all modifiers and special rules

Your Armor Class Results

Base AC: 0
Dexterity Modifier: +0
Shield Bonus: +0
Special Features: None
Magic Bonus: +0
Other Bonuses: +0
Total AC: 0

Comprehensive Guide to Calculating Armor Class in D&D 5e

Armor Class (AC) is one of the most fundamental mechanics in Dungeons & Dragons 5th Edition. It represents your character’s ability to avoid being hit by attacks, combining armor, dexterity, shields, and special abilities. Understanding how to calculate AC properly can mean the difference between a long, heroic career and an untimely demise at the hands of a lucky goblin.

The AC Formula

The basic formula for calculating AC in D&D 5e is:

AC = Base Armor Value + Dexterity Modifier + Shield Bonus + Magic Bonus + Other Bonuses

Armor Types

  • No Armor: 10 + Dex modifier
  • Light Armor: Varies (11-12) + full Dex modifier
  • Medium Armor: Varies (12-15) + Dex modifier (max +2)
  • Heavy Armor: Varies (16-18) – no Dex bonus
  • Shields: +2 to AC (requires an action to don/doff)

Dexterity Limits

  • Light armor: Full Dex bonus applies
  • Medium armor: Max +2 Dex bonus
  • Heavy armor: No Dex bonus
  • Shields: Don’t affect Dex limits
  • Unarmored Defense: Some classes get special AC calculations

Step-by-Step AC Calculation

  1. Determine Base Armor Value

    Select your armor type from the options. Each armor type has a base AC value:

    Armor Type Base AC Dex Bonus Strength Requirement Cost
    No Armor 10 Full None 0 gp
    Padded 11 Full None 5 gp
    Leather 11 Full None 10 gp
    Studded Leather 12 Full None 45 gp
    Hide 12 Max +2 None 10 gp
    Chain Shirt 13 Max +2 None 50 gp
    Scale Mail 14 Max +2 None 50 gp
    Breastplate 14 Max +2 None 400 gp
    Half Plate 15 Max +2 None 750 gp
    Ring Mail 14 None None 30 gp
    Chain Mail 16 None 13 Str 75 gp
    Splint 17 None 15 Str 200 gp
    Plate 18 None 15 Str 1,500 gp
  2. Add Dexterity Modifier

    The Dexterity modifier is added to most armor types, with restrictions:

    • Light armor: Full Dexterity modifier applies
    • Medium armor: Maximum +2 Dexterity modifier
    • Heavy armor: No Dexterity modifier
    • Shields: Don’t affect Dexterity limits
    • Natural armor (like from the Dragon Hide spell): Typically full Dexterity

    Remember that some class features (like the Monk’s Unarmored Defense or Barbarian’s Unarmored Defense) calculate AC differently, potentially using Constitution or Wisdom modifiers instead of or in addition to Dexterity.

  3. Add Shield Bonus

    A shield typically provides a +2 bonus to AC. Some magical shields may provide additional bonuses:

    • Standard shield: +2 AC
    • Shield +1: +3 AC (base +2 + magic +1)
    • Shield +2: +4 AC
    • Shield +3: +5 AC
    • Shield of Missiles: +2 AC and immunity to Magic Missile
    • Animated Shield: +2 AC and can be animated as a bonus action

    Note that donning or doffing a shield requires an action, so you can’t switch shields in the middle of combat without using your action.

  4. Add Magic Bonuses

    Magic armor and shields can provide additional bonuses:

    • +1 armor/shield: +1 AC
    • +2 armor/shield: +2 AC
    • +3 armor/shield: +3 AC
    • Adamantine armor: No AC bonus, but critical hits become normal hits
    • Mithral armor: No AC bonus, but removes Strength requirements and disadvantage on Stealth
    • Dragon Scale Mail: 14 + Dex (max +2) plus other benefits

    These bonuses stack with all other AC components unless specifically stated otherwise in the item description.

  5. Add Other Bonuses

    Various features, feats, and magic items can provide additional AC bonuses:

    • Ring of Protection: +1 AC
    • Cloak of Protection: +1 AC (and to saving throws)
    • Defensive Duelist feat: Add proficiency bonus to AC against one attack per reaction
    • Dodge action: Attackers have disadvantage on attacks against you until your next turn
    • Bladesong (Wizard): Add Intelligence modifier to AC for 1 minute
    • Heavily Armored feat: +1 AC when wearing heavy armor
    • Moderately Armored feat: +1 AC when wearing medium armor
    • Barbarian’s Unarmored Defense: 10 + Dex + Con
    • Monk’s Unarmored Defense: 10 + Dex + Wis
  6. Calculate Total AC

    Add all components together to get your final AC. Remember that:

    • Bonuses from different sources generally stack unless they’re from the same source (e.g., you can’t wear two rings of protection)
    • Some bonuses are temporary (like from the Dodge action or Bladesong)
    • AC can’t be reduced below 10 (even with penalties)
    • Some creatures have abilities that ignore certain types of AC bonuses

Special AC Calculations

Unarmored Defense

Several classes have special unarmored defense calculations:

  • Barbarian: AC = 10 + Dex modifier + Constitution modifier
  • Monk: AC = 10 + Dex modifier + Wisdom modifier
  • Wizard (Bladesinging): AC = 12 + Dex modifier (or 15 + Dex if using Bladesong)
  • Dragon Sorcerer: AC = 13 + Dex modifier when not wearing armor

These replace the standard AC calculation when not wearing armor (though some allow shields).

Multiclassing Considerations

When multiclassing, you can choose which unarmored defense to use:

  • Barbarian/Monk: Can use either calculation, but not both
  • Monk/Wizard: Can use Monk’s Unarmored Defense or Bladesong, but not both simultaneously
  • Fighter (Eldritch Knight)/Wizard: Can use Mage Armor (13 + Dex) if known

Always choose the calculation that gives you the highest AC for your current ability scores.

Common AC Mistakes to Avoid

  1. Forgetting Dexterity Limits

    One of the most common mistakes is applying the full Dexterity modifier to medium or heavy armor. Remember:

    • Light armor: Full Dex bonus
    • Medium armor: Max +2 Dex bonus
    • Heavy armor: No Dex bonus
  2. Double-Counting Bonuses

    Some bonuses don’t stack. For example:

    • You can’t benefit from both Unarmored Defense and wearing armor
    • Multiple sources of the same named bonus (like two rings of protection) don’t stack
    • The Dodge action doesn’t increase your AC – it imposes disadvantage on attacks against you
  3. Ignoring Strength Requirements

    Heavy armor often has Strength requirements. If you don’t meet them:

    • Your speed is reduced by 10 feet
    • You have disadvantage on ability checks, saving throws, and attack rolls that involve Strength or Dexterity

    Mithral armor removes these penalties while keeping the AC benefit.

  4. Forgetting About Shields

    A +2 bonus to AC is significant. Many players forget:

    • Shields can be donned or doffed as an action
    • Some class features (like Two-Weapon Fighting) require a free hand
    • Magical shields can provide additional benefits beyond AC
  5. Misapplying Temporary Bonuses

    Some AC bonuses are temporary or situational:

    • Defensive Duelist applies to one attack as a reaction
    • Bladesong lasts for 1 minute (10 rounds)
    • The Dodge action lasts until your next turn
    • Some magic items have limited uses per day

AC Optimization Strategies

For characters who want to maximize their AC, consider these strategies:

Early Game (Levels 1-4)

  • Start with the highest Dexterity you can (16+ for most classes)
  • Use studded leather (12 + Dex) for light armor classes
  • Take the Moderately Armored feat if you want medium armor
  • Consider a shield for +2 AC (unless you need two hands for weapons)
  • Magic items like +1 shields or cloaks of protection are great early finds

Mid Game (Levels 5-10)

  • Half plate (15 + Dex max 2) becomes available
  • Consider the Resilient (Dexterity) feat to boost Dex and get proficiency in Dex saves
  • Magic armor becomes more available (+1 studded leather is 13 + full Dex)
  • Feats like Defensive Duelist can provide situational AC boosts
  • Class features like Bladesong (Wizard) can provide significant temporary AC boosts

Late Game (Levels 11-20)

  • Plate armor with +3 enhancement gives 21 AC
  • Combine with a +3 shield for 23 AC
  • Legendary items can push AC even higher
  • Feats like Heavily Armored can add +1 to heavy armor AC
  • High-level class features may provide additional AC benefits
  • Consider multiclassing for better unarmored defense options

AC by Class: What to Aim For

Class Early Game Target AC Mid Game Target AC Late Game Target AC Recommended Approach
Barbarian 14-16 16-18 18-20 Unarmored Defense (Dex + Con) with shield, or medium armor
Bard 14-15 16-17 18-19 Light armor + shield, consider Moderately Armored feat
Cleric 16-18 18-19 20+ Heavy armor + shield, or medium armor if Dex is high
Druid 13-15 15-17 17-19 Light/medium armor (no metal), Wild Shape provides natural armor
Fighter 16-18 18-19 20+ Heavy armor + shield, or medium armor if Dex is high
Monk 14-16 16-18 18-20 Unarmored Defense (Dex + Wis), no shield
Paladin 16-18 18-19 20+ Heavy armor + shield, Aura of Protection helps
Ranger 14-16 16-17 18-19 Light/medium armor, consider shield if not using two weapons
Rogue 14-15 15-16 17-18 Light armor, avoid shields (need free hand for Sneak Attack)
Sorcerer 12-14 14-16 16-18 Light armor or Mage Armor, Draconic Bloodline gets natural armor
Warlock 13-15 15-17 17-19 Light armor + shield, or medium armor with Moderately Armored
Wizard 12-14 14-16 16-18 Mage Armor (13 + Dex), Bladesong adds Int modifier

AC and Game Balance

While high AC is valuable, it’s important to consider game balance:

  • Bounded Accuracy: D&D 5e uses bounded accuracy, meaning AC above 20 becomes increasingly less valuable as attack bonuses cap out around +11 to +13 for most monsters.
  • Opportunity Cost: Investing heavily in AC often means sacrificing other capabilities. A fighter with 22 AC might deal less damage than one with 18 AC but better weapons.
  • Save or Suck: Many high-level threats bypass AC with saving throws. A high AC character might still fail against a dragon’s breath weapon or a lich’s spells.
  • Action Economy: Some AC boosts (like the Dodge action) cost your action, which could be used for attacks or other abilities.
  • Magic Items: The game assumes characters will find magic items. A level 10 character with +1 armor and +1 shield having 20 AC is reasonable, while one with 24 AC might be overpowered.

As a general rule, aim for an AC that’s about 5 points higher than the typical attack bonus of enemies you’ll face. In most campaigns, this means:

  • Levels 1-4: AC 14-16
  • Levels 5-10: AC 16-18
  • Levels 11-16: AC 18-20
  • Levels 17-20: AC 20-22

Advanced AC Tactics

  1. Situational AC Boosts

    Some abilities provide temporary AC increases:

    • Defensive Duelist (Fighting Style): Add proficiency bonus to AC against one attack per reaction
    • Bladesong (Wizard): Add Intelligence modifier to AC for 1 minute
    • Shield Spell: +5 to AC until next turn (reaction)
    • Dodge Action: Attackers have disadvantage on attacks against you
    • Cover: +2 to +5 AC bonus from half to three-quarters cover

    Use these when you expect to be targeted by powerful attacks.

  2. AC Stacking with Saves

    Some abilities improve both AC and saving throws:

    • Cloak of Protection: +1 to AC and saving throws
    • Ring of Protection: +1 to AC and saving throws
    • Paladin’s Aura of Protection: Add Charisma modifier to saving throws (but not AC)
    • Barbarian’s Danger Sense: Advantage on Dex saves (but not AC)
  3. AC and Mobility

    High AC is even more valuable when combined with mobility:

    • High Dexterity improves initiative and AC
    • Mobile feat allows you to move after attacks without opportunity attacks
    • Cunning Action (Rogue) allows Disengage as a bonus action
    • Misty Step (spell) can help you reposition

    A mobile character with high AC is very hard to pin down.

  4. AC Against Specific Threats

    Some enemies have ways to bypass AC:

    • Magic Weapons: Many monsters have attacks that are magical and can bypass non-magical armor resistances
    • Save-based Effects: Dragons’ breath weapons, spells like Fireball, and many high-level monster abilities require saving throws
    • Legendary Actions: Some creatures can make multiple attacks per round, making high AC more valuable
    • Advantage: Many monsters have abilities that give them advantage on attacks (like the Pack Tactics of wolves)

    Consider having contingency plans for when AC isn’t enough.

Frequently Asked Questions About AC

  1. Does AC affect saving throws?

    No, AC and saving throws are separate mechanics. AC is used against attack rolls, while saving throws are used against spells and special abilities that don’t require attack rolls.

  2. Can you have negative AC?

    No, the lowest possible AC is 10 (for a completely unarmored character with a -5 Dexterity modifier).

  3. Does AC affect touch attacks?

    In D&D 5e, there are no “touch attacks” as a separate mechanic. All attacks are resolved against AC, though some spells require attack rolls while others require saving throws.

  4. How does AC work with grappling?

    Grappling uses an attack roll against AC to initiate, but maintaining a grapple uses Athletics checks contested by the target’s Athletics or Acrobatics checks (not AC).

  5. Does AC affect opportunity attacks?

    Yes, opportunity attacks are resolved like any other melee attack, using the attacker’s attack roll against the target’s AC.

  6. Can you have fractional AC?

    No, all AC bonuses are whole numbers. If you have a +0.5 modifier from an odd ability score, it doesn’t apply to AC (only to skills and attacks).

  7. Does AC affect spells that require attack rolls?

    Yes, spells like Magic Missile (which doesn’t require an attack roll in 5e) automatically hit, but spells like Fire Bolt or Eldritch Blast use attack rolls against AC.

Official Resources and Further Reading

For more official information on Armor Class in D&D 5e, consult these authoritative sources:

For academic perspectives on game design and mechanics (including AC systems), these resources may be of interest:

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