Armor Class (AC) is a derived statistic in Fallout, Fallout 2, and Fallout Tactics: Brotherhood of Steel. In J.E. Sawyer's Fallout Role-Playing Game, it was renamed Evade.
Armor class is a modifier to the chance to hit, applied to the attacker's chance to hit after all other modifiers are applied.
E.g. the target has an AC of 15, while the attacker has a 65% chance to hit. The AC is substracted from the 65, reducing the chance to hit to 50%.
The Armor Class is determined by a combination of Agility, armor, and any traits/perks the player has:
- Base AC is equal to the character's Agility.
- Kamikaze (trait) sets it to 0 regardless of the agility score.
- The base agility is supplemented by the equipped armor's AC.
- Dodger (perk) adds 5 to AC.
- At the end of each turn in combat, any leftover Action Points are added to the AC for the duration of the enemy turn.
- HtH Evade (perk) doubles the AC bonus and then adds 1/12 of the character's Unarmed skill on top of that.