Armor Class (AC)

Represents how difficult it is to hit a creature with an attack.

Base AC (Unarmored) = 10 + Dexterity Modifier
Wearing Armor: AC = Based on armor type + Dexterity Modifier (if allowed by the armor).
  Light Armor: Full Dexterity Modifier
  Medium Armor: Max (+2) Dexterity Modifier
  Heavy Armor: No Dexterity Modifier
Shield: +2 AC if a shield is equipped.
Unarmored Defense (Monk/Barbarian):
  Monk: (10 + Dex Mod + Wis Mod)
  Barbarian: (10 + Dex Mod + Con Mod)