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.

Combat Damage

 * DMG = Base Weapon Damage, or what you see on the Pip Boy (normally)
 * This number will automatically include perks such as Ghoul Ecology, Superior Defender, Demolition Expert, and Pyromaniac
 * CD = Critical Damage, which you may have to look up on the weapon's page
 * TP = Total weapon projectiles, which you may have to look up on the weapon's page
 * TPH = Total weapon projectiles which strike the target area
 * BCP = Better Critical Perk, which will be 1.5 if a critical occurs
 * SM = Sneak Modifier, which is always 2.0
 * AM = Appendage Modifier, for heads it is 2.0, for other limbs it is 1.5
 * DR = Damage Reduction, which is equal to the armor rating of the target area

Critical Damage (CD) will be equal to 0.0 if a critical does not occur. Better Critical Perk (BCP) will be equal to 1.0 if a critical does not occur, or if you do not have the perk. Torso shots receive an Appendage Modifier (AM) value of 1.0. The Sneak Modifier (SM) will be equal to 1.0 if you are currently detected by the target or if the target is actively looking for you.

The damage formula is calculated as follows:

[(DMG/TP)xTPH+(TPxCD)-DR]xBCPxSMxAM = (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.
 * When dealing with multiple-projectile weapons, you have to use this equation seperately for each body area because the TPH will differ for each equation

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 1320. If the player further increases the damage via a Headshot, then that damage doubles again to 2680, enough to one-shot a Super Mutant Behemoth!
 * [80+(9*40)]*(1.5)*(2.0)*(2.0) = 2680 damage possible

Example 2
The Alien Blaster is a rare item which always does critical hits. Looking on the Pip Boy, it currently appears to have a 110 Base Damage value. Critical hits with this weapon do additional damage equal to the base damage, in this case 110. The shot is fired at a Super Mutant Behemoth's leg at close range, while the player is detected. The player does not have the Better Criticals Perk. The target's armor rating is unknown.


 * [(110+(1*110)-0.0]*(1.0)*(1.0)*(1.5) = 330 damage possible

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.