I DnD5, under resp. klass i PHB:
Barbarian unarmored defense: while not wearing armor, AC = DEX-mod. + CON-mod., you can use shield.
Monk unarmored defense: while not wearing armor, AC = DEX-mod. + WIS-mod.
Under Equipment, armor i PHB ger varje rustning ett fast AC + DEX-mod., ex:
Studded...