How To Calculate Armor Class 5E

Calculate your character’s Armor Class (AC) with all possible modifiers in Dungeons & Dragons 5th Edition

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 other protective measures. 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 Armor Class in D&D 5e is:

AC = Base AC + Dexterity Modifier + Shield Bonus + Magic Item Bonus + Other Modifiers

1. Base Armor Class

Your base AC depends on what type of armor you’re wearing (if any). Here’s the complete breakdown:

Armor Type	Base AC	Dex Bonus	Strength Requirement	Stealth Disadvantage
No Armor	10	Full	None	No
Padded	11	Full	None	Yes
Leather	11	Full	None	No
Studded Leather	12	Full	None	No
Hide	12	Max +2	None	No
Chain Shirt	13	Max +2	None	No
Scale Mail	14	Max +2	None	Yes
Breastplate	14	Max +2	None	No
Half Plate	15	Max +2	None	Yes
Ring Mail	14	None	None	Yes
Chain Mail	16	None	13 Str	Yes
Splint	17	Max +2	15 Str	Yes
Plate	18	None	15 Str	Yes

2. Dexterity Modifier

Your Dexterity modifier is added to your AC unless you’re wearing heavy armor or a shield that restricts Dexterity bonuses. The maximum Dexterity bonus you can apply depends on the armor type:

• Light Armor: Full Dexterity bonus applies
• Medium Armor: Maximum +2 Dexterity bonus
• Heavy Armor: No Dexterity bonus
• Shields: Don’t affect Dexterity bonus limits

Remember that some armors (like studded leather) give both a base AC and allow full Dexterity bonuses, making them excellent choices for dexterous characters.

3. Shield Bonus

A shield provides a +2 bonus to AC, regardless of other factors. This stacks with all armor types and other bonuses. The most common shields are:

• Shield: +2 AC, no strength requirement, doesn’t impose disadvantage on Stealth
• Magic Shields: Can provide additional bonuses (e.g., +1, +2, or +3)

Note that using a shield requires a free hand, and some class features (like the Dual Wielder feat) allow you to use two weapons while still gaining the shield’s AC bonus.

4. Magic Item Bonuses

Magic armor and shields can provide additional bonuses to AC. These bonuses stack with all other AC calculations unless specified otherwise. Common magic item bonuses include:

• +1 Armor/Shield: +1 to AC
• +2 Armor/Shield: +2 to AC (rare)
• +3 Armor/Shield: +3 to AC (very rare)
• Cloak of Protection: +1 to AC and saving throws
• Ring of Protection: +1 to AC and saving throws

Some magic items provide conditional bonuses. For example, the Bracers of Defense give +2 to AC but only if you’re not wearing armor or using a shield.

5. Other Modifiers

Several other factors can modify your AC:

• Fighting Styles:
  • Defense: +1 to AC
  • Protection: When an attacker you can see attacks a target other than you within 5 feet, you can use your reaction to impose disadvantage (effectively giving your ally +4 to AC against that attack)
• Cover:
  • Half Cover: +2 to AC
  • Three-Quarters Cover: +5 to AC
  • Total Cover: Can’t be targeted
• Dodge Action: Until your next turn, attackers have disadvantage on attacks against you (effectively +4 to AC)
• Class Features:
  • Barbarian’s Unarmored Defense: AC = 10 + Dex + Con
  • Monk’s Unarmored Defense: AC = 10 + Dex + Wis
  • Draconic Bloodline Sorcerer: AC = 13 + Dex
• Feats:
  • Heavy Armor Master: +1 to AC when wearing heavy armor
  • Medium Armor Master: +1 to AC when wearing medium armor (and removes Dex cap)
  • Lightly Armored: Gain proficiency with light armor
  • Moderately Armored: Gain proficiency with medium armor and shields

Special Cases and Exceptions

Some situations modify AC in unique ways:

1. Prone: Attackers within 5 feet have advantage (effectively -4 to AC), while attackers beyond 5 feet have disadvantage (+4 to AC)
2. Restrained: Attackers have advantage against you (-4 to AC)
3. Incapacitated: Attackers have advantage against you (-4 to AC)
4. Blinded: Attackers have advantage against you (-4 to AC)
5. Invisible: Attackers have disadvantage against you (+4 to AC) unless they can sense you without sight
6. Frightened: If the source of fear is within line of sight, attackers have advantage (-4 to AC)

AC by Character Type

Different character builds will approach AC differently. Here’s how various archetypes typically calculate their AC:

Character Type	Typical AC Calculation	Example AC at Level 5	Strengths	Weaknesses
Heavy Armor Warrior	Plate (18) + Shield (+2) + Magic (+1)	21	Highest possible AC, no Dex dependency	Heavy, expensive, Stealth disadvantage
Dexterous Skirmisher	Studded Leather (12) + Dex (+3) + Shield (+2)	17	Good mobility, no Stealth penalty	Lower maximum AC than heavy armor
Unarmored Monk	10 + Dex (+3) + Wis (+3)	16	No armor cost, scales with Wis	Lower than armored options
Spellcaster	Mage Armor (13) + Dex (+2)	15	No armor proficiency needed	Vulnerable if Mage Armor drops
Dual-Wielding Rogue	Leather (11) + Dex (+4) + Dual Wielder (+1)	16	High damage output, good AC	No shield bonus

Common AC Mistakes

Avoid these frequent errors when calculating AC:

1. Adding Dexterity to heavy armor: Heavy armor provides its full AC regardless of Dexterity
2. Exceeding medium armor’s Dex cap: Medium armor only allows a maximum +2 Dexterity bonus unless you have the Medium Armor Master feat
3. Double-counting shields: The shield bonus is already included in some armor descriptions (like the “Shield” option in our calculator)
4. Forgetting magic bonuses: A +1 shield and +1 armor stack for a total +2 bonus
5. Ignoring temporary modifiers: Effects like the Dodge action or cover bonuses are situational but powerful
6. Miscounting unarmored defense: Barbarians and Monks calculate AC differently from standard rules

Optimizing Your AC

To maximize your AC, consider these strategies:

• For melee characters: Plate armor + shield + Defense fighting style can reach 20 AC without magic items
• For dexterous characters: Studded leather + high Dexterity + shield offers excellent protection with mobility
• For spellcasters: Mage Armor + high Dexterity + Shield spell (when needed) provides solid defense
• Feat selection: Heavy Armor Master or Medium Armor Master can significantly boost AC
• Magic items: Prioritize +1/+2/+3 armor and shields before other magic items
• Tactical positioning: Use cover and the Dodge action when expecting heavy attacks

AC in Different Editions

Armor Class has evolved across D&D editions:

• Original D&D (1974): AC started at 9 (best) and went down to 0 (worst)
• AD&D (1977): Introduced descending AC (lower was better) from 10 to -10
• D&D 3e (2000): Switched to ascending AC (higher is better) starting at 10
• D&D 4e (2008): AC became one of several defenses (along with Fortitude, Reflex, Will)
• D&D 5e (2014): Returned to simplified AC system similar to 3e but with bounded accuracy

The current 5e system strikes a balance between simplicity and tactical depth, making AC calculations intuitive while still offering meaningful choices for character optimization.

Official Resources

For authoritative information on Armor Class calculations, consult these official sources:

• Official D&D 5e Rules (Wizards of the Coast)
• D&D Beyond Equipment Database
• Role-Playing Games Stack Exchange (Community Q&A)

For academic perspectives on game mechanics and their psychological impacts, you might explore:

• Game Studies Journal (Academic research on game design)
• UC Berkeley Institute for Game Studies