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Chapter 8: Tactical Rules / Combat Basics

Armor Class (AC)

Source Starfinder Core Rulebook pg. 240
Your Armor Class (AC) represents how hard it is for opponents to land a solid damaging blow on you. Your Armor Class (AC) is the minimum attack roll result that an opponent needs to hit you and deal damage. Armor Class is divided into two categories: Energy Armor Class (EAC) and Kinetic Armor Class (KAC). Any reference to Armor Class, including bonuses and penalties, applies to both EAC and KAC unless otherwise specified.

Your EAC and KAC are primarily determined by your armor bonus (most often from a suit of armor you wear) plus your Dexterity modifier. Calculate your EAC and KAC using the following formula: 10 + your armor’s EAC or KAC armor bonus (whichever is appropriate) + your Dexterity modifier.

Most suits of armor provide separate armor bonuses to EAC and KAC. However, some suits of armor’s conditions prevent you from using your full Dexterity bonus. Various other bonuses can apply from class features, feats, special circumstances, and so on. For more information on bonuses, see page 266.

Energy Armor Class (EAC)

Your Energy Armor Class (EAC) represents the defenses you have against attacks that only deal damage as a result of some kind of energy (such as acid, cold, electricity, fire, or sonic damage). When an opponent’s attack would deal only energy damage (if he is using, for example, a laser pistol), his attack roll result is compared to your EAC to determine whether he hits you. Some weapons and effects that use magical or exotic untyped energies might also target your EAC; the description of the weapon or effect tells you if this is the case.

Kinetic Armor Class (KAC)

Your Kinetic Armor Class (KAC) represents the defenses you have against attacks that primarily deal damage as a result of a physical impact. This generally includes attacks that deal bludgeoning, piercing, or slashing damage (described as “kinetic attacks”), attacks that don’t otherwise specify which AC they target, impacts from falling, and damage from crushing or constriction. When a foe’s attack would deal such damage (if he is using, for example, a starknife), even if it also deals energy damage, his attack roll result is compared to your KAC to determine whether he hits.