Fallout 3 combat

Fallout 3 has a significantly different combat system than its predecessors, in some ways more complex because of the fully 3D environment.

VATS
The Vault-Tec Assisted Targeting System, or V.A.T.S., is a queuing system, inspired partly by the ability to shoot specific body parts in the turn-based combat system of Fallout and Fallout 2.

While using V.A.T.S., the otherwise real-time combat is paused. Various actions cost action points, and both the player and enemies can target specific body areas for attacks, inflicting specific injuries.

Combat Damage

 * DMG = Unmodified base damage per weapon discharge (single click of mouse)
 * CRITDMG = Unmodified bonus damage added for critical strike on target, per projectile
 * Crit% = Gun crit multiplier x 33% base crit rate (10 luck + Finesse + Survival Guru + VATS modifier)
 * TP = Number of projectiles per weapon discharge (single click of mouse)
 * SA = Sneak Attack modifier adds +100% total damage
 * BC = Better Criticals modifier adds +50% critical damage
 * HS = Headshot modifier adds +100% total damage
 * Male Target = SA + BC + HS + Bloody Mess perk + Black Widow perk + Yao Guai Meat + Psycho + "Very Hard" difficulty
 * Non-Male Target = Same as male target only no Black Widow perk
 * Insect = Same as non-male, only HS modifier is replaced with Entomologist perk
 * AP = Action point cost per round
 * DMG/Round = Modified damage per VATS round including Better Criticals, Xenotech Expert perk, Pyromaniac perk, and maximum hit chance of 95%
 * DMG/Full VATS = Modified damage for max number of rounds given total AP (135) and AP cost of weapon with mods for Bloody Mess, Yao Guai Meat, Psycho, and "Very Hard" difficulty
 * AP Next = AP needed for next shot after Full VATS

The damage formula is calculated as follows:
 * $$(\text{DMG}+(\text{TP}\times\text{CRITDMG}\times\text{BC}))\times\text{SA}\times\text{HS}=\text{Final Damage to Target}$$


 * This equation does not deal with the hit probabilities, or the critical probability. It is strictly used to calculate damage dealt to target -- real or possible.

Example 1
The Terrible Shotgun is one of the most powerful weapons in the game. While in perfect condition, and with a Small Guns skill of 100, the weapon deals 80 damage, plus an extra 40 damage for a critical hit. However, this weapon fires 9 pellets. Because of this, when the weapon is fired outside of V.A.T.S. and scores a critical hit, the critical hit for each pellet is counted individually. This means that (if all pellets make contact), the weapon will deal 440 damage (80 base damage, plus 9 extra 40 critical damages). In Sneak Mode, this damage is doubled, increasing it to 880 points of damage. And if the player has the Better Criticals perk, the damage will increase to 1240. If the player further increases the damage via a Headshot, then that damage doubles again to 2480, enough to one-shot a Super Mutant Behemoth!


 * NOTE: These tables do not account for perks such as Ghoul Ecology, Superior Defender, Demolition Expert, and Pyromaniac. These four perks modify the base damage (DMG).