Armor Class

DnD SRD (Index) :: BasicRules (Table Of Contents | List Of Tables) :: Armor Class

Sections:

..Dexterity modifier
..Size modifier
..Stacking modifiers

Tables:

Armor Class

This material is Open Game Content, and is licensed for public use under the terms of the Open Game License v1.0a.

Every character (and items in some circumstances) have an Armor Class (AC). The base AC for a medium-sized character or item is 10. Bonuses and penalties are applied to this basic Armor Class to reflect the effects of armor, dexterity, etc.
Armor Class is an indication of how difficult it is to hit and do damage to a target.

Dexterity modifier

Apply a character's Dexterity modifier to the character's Armor Class any time that character can physically react to an attack. Characters lose their Dexterity modifier when they are flat-footed, unaware of an attacker, or when they are restrained or otherwise rendered immobile.

Size modifier

A character's size generates a standard Armor Class modifier, per this table:

Armor Class Modifiers

Size	AC/Attack Modifier
Fine	+8
Diminutive	+4
Tiny	+2
Small	+1
Medium	0
Large	-1
Huge	-2
Gargantuan	-4
Colossal	-8

Stacking modifiers

AC modifiers of the same type do not stack, except:

Armor bonuses from armor and shields
Enhancement bonuses from armor and shields
Dodge bonuses
Circumstance bonuses

DnD SRD (Index) :: BasicRules (Table Of Contents | List Of Tables) :: Armor Class