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Armor Class (AC)

Armor Class represents how hard you are to hit. Attacks must meet or exceed your AC to hit you.

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How Armor Class WorksArmor Types and ACAlternative AC CalculationsWays to Improve ACCommon MistakesDM Tips

How Armor Class Works

When an attack targets you, the attacker rolls d20 + modifiers. If the total equals or exceeds your AC, the attack hits.

Base AC Calculations:

  • Unarmored: 10 + Dexterity modifier
  • Light Armor: Armor base + Dexterity modifier
  • Medium Armor: Armor base + Dexterity modifier (max +2)
  • Heavy Armor: Armor base (no Dex)

Shields: +2 AC (requires proficiency)

Armor Types and AC

ArmorACDex BonusStealth
Light Armor
Padded11FullDisadvantage
Leather11Full—
Studded Leather12Full—
Medium Armor
Hide12Max +2—
Chain Shirt13Max +2—
Scale Mail14Max +2Disadvantage
Breastplate14Max +2—
Half Plate15Max +2Disadvantage
Heavy Armor
Ring Mail14NoneDisadvantage
Chain Mail16NoneDisadvantage
Splint17NoneDisadvantage
Plate18NoneDisadvantage

Alternative AC Calculations

Some features provide alternative AC calculations. You can only use ONE at a time:

Class Features:

  • Barbarian Unarmored Defense: 10 + Dex + Con
  • Monk Unarmored Defense: 10 + Dex + Wis
  • Draconic Sorcerer: 13 + Dex (no armor)

Spells:

  • Mage Armor: 13 + Dex (no armor)
  • Barkskin: AC can't be less than 16

Important: Alternative calculations don't stack. Choose the best one. Shields and other AC BONUSES stack with any calculation.

Ways to Improve AC

Equipment:

  • Better armor
  • Shield (+2)
  • Magic armor (+1, +2, +3)
  • Magic shields (+1, +2, +3)

Spells (Bonuses):

  • Shield (reaction): +5 AC until next turn
  • Shield of Faith: +2 AC for 10 minutes
  • Haste: +2 AC

Other Sources:

  • Fighting Style (Defense): +1 AC in armor
  • Cloak/Ring of Protection: +1 AC each
  • Cover: +2 (half) or +5 (three-quarters)

Common Mistakes

Common Mistake
Stacking multiple AC calculations instead of choosing one
Common Mistake
Forgetting medium armor caps Dex bonus at +2
Common Mistake
Not knowing heavy armor has Strength requirements
Common Mistake
Forgetting shields require proficiency to use effectively

DM Tips

DM Tip
AC 15 is a reasonable baseline for most encounters
DM Tip
Very high AC (20+) can make combat tedious
DM Tip
Remember to use saving throw spells against high-AC targets
DM Tip
Cover is often forgotten but very impactful