Fallout and Fallout 2 combat



Combat in Fallout and Fallout 2 is resolved in turns, based on the statistics of the participatants.

Sequence and actions
The order in which combat actors act is determined by Sequence. The higher the Sequence, the earlier will the actor's turn begin. Characters and critters which initiate combat automatically get the first turn, with subsequent turns determined by the statistic.

In combat, participants rely on Action Points to take action. See the main article for the exact method in which the Action Point pool is determined and which variables affect it.

Bonus Rate of Fire and Bonus HtH Attacks reduce the cost of ranged and melee attacks respectively by 1 AP.

The Fast Shot trait reduces ranged attack costs by 1 AP, but precludes making targeted attacks.

Close combat
The chance to hit enemies in ranged combat is determined by the following calculation (estimated). The result is expressed in percentages and cannot exceed 95%.


 * Chance to hit = Unarmed/Melee Skill - (Target AC + Aimed Shot Penalty)

Ranged combat
The chance to hit enemies in ranged combat is determined by the following calculation. The result is expressed in percentages and cannot exceed 95%.


 * Chance to hit = (Weapon Skill + (8*Perception) + Weapon Perk) - ((4*Distance to Target) + Target AC + Lighting Penalty + Aimed Shot Penalty)


 * Positive factors:
 * Weapon skill is any of the main ranged weapon skills: Small Guns, Big Guns, and Energy Weapons.
 * Perception can be modified by perks like Sharpshooter and the modified value is used for calculations.
 * Weapon Perks can be Weapon Accurate, Weapon Long Range, or Weapon Scope Range (see perk pages for precise descriptions).
 * Negative factors:
 * Each hex of distance between you and the target is a 4% penalty.
 * Target AC is deducted directly (20 AC is a -20% to hit).
 * Lighting penalties are determined as follows (in darkness):
 * Target is 1 hex away: -10%
 * Target is 2 hexes away: -25%
 * Target is 3 or more hexes away: -40%
 * Finally, aimed shots are made with penalties depending on the target area. Shooting the eyes is, of course, the hardest.

Damage calculation
The objective of combat is to reduce the opponent's hit points to 0 (zero). That's where damage comes in.

Melee combat
Damage in close combat is determined via two separate formulas. Melee Weapons damage relies on the weapon damage:


 * Melee Damage = (Minimal Weapon Damage) - (Maximum Weapon Damage + Bonus Melee Damage)

While Unarmed damage relies on basic fists damage (1 - 2) with modifiers:


 * Unarmed Damage = (1 + Unarmed Attack Bonus) - (2 + Bonus Melee Damage + Unarmed Attack Bonus).

Bonus Melee Damage is determined by the following calculation, factoring in the Heavy Handed trait and Bonus HtH Damage perk.


 * Bonus Melee Damage = (Player Strength - 5) + Heavy Handed + Bonus HtH Damage

Ranged combat
Damage calculations are fairly complex and expressed by the following code (steps bottom to top): ammoX*CM MV*Y ND=RD+RB ND=ND*(ammoX*CM) if MV*Y <= 0 then skip next step ND=ND/(MV*ammoY) ND=ND/2 ND=ND*CD ND=ND/100 ND=ND-armorDT if ND <=0 then skip for no damage, repeat loop or exit N1=ND N2=ND*armorDR+ammoDRM N2=N2/100 ND=N1-N2 if ND <=0 then skip for no damage, repeat loop or exit TD=TD+ND


 * ND = Net damage value
 * RD = Random damage value produced from weapons hit damage range
 * RB = Bonus Ranged Damage modifier (+2 or +4), otherwise 0.
 * CM = Critical hit damage multiplier (if no critical hit then CM=2, otherwise assigned value from critical hit table)
 * armorDR = Target armor Damage Resistance value.
 * armorDT = Target armor Damage Threshold value.
 * ammoX = Ammo dividend
 * ammoY = Ammo divisor
 * ammoDRM = Ammo resistance modifier (only value allowed to be negative or positive in the equation)
 * CD = Combat difficulty multiplier
 * MV = Mystery value
 * PEN = Weapon Penetrate reduces DT by 80%. As such, if the weapon has this perk, divide by 0.2. Otherwise, leave at 1.
 * RM = Ammo Damage Resistance modifier (only value allowed to be negative or positive in the equation).
 * CD = Multiplier from combat difficulty (Easy=75, Normal=100, Hard=125).

Bugged damage calculation in vanilla Fallout
Due to a bug in the executable, Fallout does not factor in ammunition modifiers into the calculation, making it much simpler:

$$ Damage = \left ( \left (RD+RB \right ) - ADT \right ) * \left ( 1 - ADR \right ) $$

Critical hits and failures
If an attacker is lucky, he may find that his attack is particularly painful for the target, potentially causing crippled limbs, damaged eyesight or even instant death. These are critical hits. When you make an attack, a derived statistic called critical chance is checked against to see if your attacking is critical. If it is, a random effect follows, which can be extra damage or more drastic outcomes.

On the flipside, there are also critical failures. If you really fumble your attack (characters with the Jinxed trait are notorious for this), something disastrous may occur. The most common result is attacking the wrong target (for instance, you may be aiming at a mutant, but you will accidentally shoot your friend who is in between you and the mutant). Other possible results include weapon jams, dropping weapons, weapon destruction, causing damage to oneself (by stabbing yourself in the foot or some such) and other unfortunate outcomes.