Wikia

Vault-Tec Labs

Fallout engine calculations

400pages on
this wiki
Talk0

Stats Edit

There are 7 basic values (stats), describing the character in Fallout. Here they are:

  • Strength (ST)
  • Perception (PE)
  • Endurance (EN)
  • Charisma (CH)
  • Intelligence (IN)
  • Agility (AG)
  • Luck (LK)

Stats are not being calculated. Each stat can have a value between 1 and 10 inclusively. The default value for all the stats is 5. Also, a player is given 5 free points to improve any of these stats at start.

Skills Edit

There are 18 skill values the character in Fallout has. Skills are being measured in percent and have a value ceiling at 300% (200% in Fallout 1). Each skill has its basic value that is being calculated by a formula derived from the stats. All fractional values are being rounded down. Here are these formulas:

Small guns:

5 + 4 * AG [Fallout 2]
35 + AG [Fallout 1]

Big guns:

2 * AG [Fallout 2]
10 + AG  [Fallout 1]

Energy weapons:

2 * AG [Fallout 2]
10 + AG  [Fallout 1]

Unarmed:

30 + 2 * (AG + ST) [Fallout 2]
65 +(ST + AG) / 2  [Fallout 1]

Melee weapons:

20 + 2 * (AG + ST) [Fallout 2]
55 + (ST + AG) / 2  [Fallout 1]

Throwing:

4 * AG [Fallout 2]
40 + AG  [Fallout 1]

First aid:

2 * (PE + IN) [Fallout 2]
30 + (PE + IN)  [Fallout 1]

Doctor:

5 + (PE + IN) [Fallout 2]
15 + (PE + IN) / 2  [Fallout 1]

Sneak:

5 + 3 * AG [Fallout 2]
25 + AG  [Fallout 1]

Lockpick:

10 + (PE + AG) [Fallout 2]
20 + (PE + AG) / 2  [Fallout 1]

Steal:

3 * AG [Fallout 2]
20 + AG  [Fallout 1]

Traps:

10 + (PE + AG) [Fallout 2]
20 + (PE + AG) / 2  [Fallout 1]

Science:

4 * IN [Fallout 2]
25 + 2 * IN  [Fallout 1]

Repair:

3 * IN [Fallout 2]
20 + IN  [Fallout 1]

Speech:

5 * CH [Fallout 2]
25 + 2 * CH  [Fallout 1]

Barter:

4 * CH [Fallout 2]
20 + 2 * CH  [Fallout 1]

Gambling:

5 * LK [Fallout 2]
20 + 3 * LK  [Fallout 1]

Outdoorsman:

2 * (EN + IN) [Fallout 2]
5 + (EN + IN) / 2  [Fallout 1]

The twelve non-combat skills are increased by 20 on Easy difficulty, and decreased by 10 on Hard difficulty.

Every experience level up a player will get

5 + 2 * IN

skill points for skill improvements. The more value has the skill the harder it is to improve:

0% - 100% : 1% further costs 1 skill point
101% - 125% : 1% further costs 2 skill points
126% - 150% : 1% further costs 3 skill points
151% - 175% : 1% further costs 4 skill points
176% - 200% : 1% further costs 5 skill points
201% - 300% : 1% further costs 6 skill points

In Fallout 1, it always costs 1 skill point to increase a skill.

Tag Skills Edit

A player must choose (tag) any 3 of the skills as their primary skills at start. Tagging adds a permanent bonus of 20% to a skill and doubles its improvement score. On the experience level 12, a player can take a perk which allows them to tag another one untagged skill.

Misc Edit

There are some miscellaneous parameters for a player in Fallout that cannot be changed directly. All values must be positive or equal to zero (with the except for Healing rate and Melee damage). The misc parameters are calculated based on the stats as well. All fractional values are being rounded down.

Hit points:

15 + 2 * EN + ST
Every time you gain a level this increases by 2 + EN / 2

Armor class:

AG

Action points:

5 + AG / 2

Carry weight:

25 + 25 * ST

Melee damage:

ST - 5
* Note that this value has a minimum value of 1.
* Note that this value is added to the maximum possible damage of an Unarmed or Melee attack. Therefore, only maximum damage potential is increased, not necessarily actual damage.
* For example, a Crowbar has an unmodified damage output of 3-10 points. If Melee damage is 4, then the Crowbar will ultimately cause 3-14 points of damage.

Damage resistance:

0

Poison resistance:

5 * EN

Radiation resistance:

2 * EN

Sequence:

2 * PE

Healing rate:

EN / 3
* Note that this value will always be at least 1.

Critical chance:

LK

Traits Edit

A player may choose up to 2 of the 16 traits at start. All traits have both positive and negative effects. Some of the effects are unknown or not obvious and are not yet figured out. Here are the known trait effects:

Fast metabolism:

Healing rate +2
Radiation and poison resistances = 0

Bruiser:

ST +2
Action Points -2

Small frame:

AG +1
Carry weight is calculated as 25 + ST * 15

One hander:

Increased chance to hit with one-handed weapons (by 20%)
Decreased chance to hit with two-handed weapons (by 40%)

Finesse:

Critical chance +10%
+30% DR to all attacks
(Like damage resistance from armor and ammo modifiers, this is ignored by armor-bypassing criticals)

Kamikaze:

Sequence +5
Armor class = 0

Heavy handed:

Melee damage +4
-30 penalty to critical hit table rolls

Fast shot:

-1 action point required to fire
Aimed shots are disabled

Bloody mess:

People die with the bloodiest death animations allowed by violence level preference

Jinxed:

All misses have a 50% chance to be "upgraded" to a critical failure.
That includes other NPCs too.

Good natured:

+15 first aid, doctor, speech and barter
-10 small guns, big guns, energy weapons, unarmed, melee weapons and throwing

Chem reliant:

Addiction time reduced by 50%
Addiction chance increased by ?

Chem resistant:

Chem affect duration reduced by 50%
Addiction chance reduced by 50%

Sex appeal:

Sex appeal value raised for NPCs of opposite gender; reduced for same gender. 

No obvious penalties; used in many script checks

Night person:

+1 PE and AG at night
-1 PE and AG during daylight
* Replaced by Sex appeal in Fallout2

Skilled:

+5 skill points per level
Perk gain every 4 levels

Gifted:

+1 all stats
-10 all skills
-5 skill points gain every level

Perks Edit

Awareness

See detailed critter information (current HP, weapon, if crippled (but not which limb is crippled)).

Bonus HtH Attacks

-1 AP for HtH and melee attacks.

Bonus HtH Damage

+2 Melee damage per rank (3)

Bonus Move

+2 AP that can only be used for movement per rank (2)

Bonus Ranged Damage

+2 ranged damage per rank (2)

Bonus Rate of Fire

-1 AP for ranged weapons

Earlier Sequence

+2 Sequence per rank (3)

Faster Healing

+2 healing rate per rank (3)

More Criticals

+5% critical chance per rank (3)

Night Vision

Reduces darkness level?

Presence

Improves NPC reactions?

Rad Resistance

+15% radiation resistance per rank (3) [Fallout 1]
+15% radiation resistance per rank (2) [Fallout 2]

Toughness

+10% to normal damage resistance per rank (3)

Strong Back

+50 carry weight per rank (3)

Sharpshooter

+2 PE when determining chance to hit?

Silent Running

Can run while sneaking.

Survivalist

+25 to Outdoorsman skill per rank (3)

Master Trader

Improves barter modifiers?

Educated

+2 skill points per level per rank (3)

Healer

First Aid and Doctor heal 4-10 more HP per rank (2)

Fortune Finder

More money found in random encounters?

Better Criticals

+20 to critical hit table rolls

Empathy

See NPC's reactions to dialogue options.

Slayer

All melee attacks are critical hits.

Sniper

Ranged attacks are critical hits if Luck check is passed.

Silent death

Cause double damage if you hit a critter in the back while sneaking.

Action Boy

+1 AP per rank (2)

Mental Block

Not affected by the Master's psychic attacks [Fallout 1 only]

Lifegiver

+4 additional HP per level per rank (2)

Dodger

+5 AC

Snakeeater

+25% poison resistance per rank (2)

Mr. Fixit

+10 to Repair and Science skills

Medic

+10 to First Aid and Doctor skills

Master Thief

+15 to Lockpick and Steal skills

Speaker

+20 to Speech skill

Heave Ho!

+2 ST for determining throwing range per rank (3)

Friendly Foe

Friendly critters highlighted in green in combat [Fallout 1 only, Fallout 2 always does this]

Pickpocket

Removes item size and critter facing penalties when stealing.

Ghost

+20 to Sneak skill in dark areas

Cult of Personality

Karma modifiers are always positive

Scrounger

More ammo in random encounters [Fallout 1 only]

Explorer

More special encounters?

Flower Child

Addiction chance reduced by 50%, addiction time reduced by 50% [Fallout 1 only]

Pathfinder

Traveling on the world map takes 25% less time per rank (2)

Animal Friend

Won't be attacked by animals [Fallout 1 only]
What types of critters count as 'animals' isn't known

Scout

Worldmap visibility range increased from 1 surrounding square to two surrounding squares
Higher chance to run into Special Encounters (by ?)

Mysterious Stranger

An ally sometimes appears in random encounters

Ranger

+15 to Outdoorsman skill

Quick Pockets

-1 AP to open inventory per rank (2) [Fallout 1]
-2 AP to open inventory [Fallout 2]

Smooth Talker

+1 IN for determining dialogue options per rank (3)

Swift Learner

+5% more experience points per rank (3)

Tag!

Choose a fourth tag skill

Mutate

Remove a trait and choose another to take its place
If you only have one trait, you will have to remove it; you can't add a second one

Gecko Skinning

Can skin dead geckos

Dermal Impact Armor

+5% to normal and explosive DR

Dermal Impact Assault Enhancements

+10% to normal and explosive DR
-1 CH

Phoenix Armor Implants

+5% to laser, fire, and plasma DR

Phoenix Assault Enhancements

+10% to laser, fire, and plasma DR
-1 CH

Vault City Inoculations

+10% to poison and radiation resistance

Adrenaline Rush

+1 ST if below 50% HP

Cautious Nature

+3 PE for determining random encounter placement

Comprehension

+50% more skill points gained from reading books

Demolition Expert

Dynamites and Plastic Explosives always go off on time
Dynamites and Plastic Explosives cause +10 damage

Gambler

+20 to Gambling skill

Gain Strength

+1 ST

Gain Perception

+1 PE

Gain Endurance

+1 EN

Gain Charisma

+1 CH

Gain Intelligence

+1 IN

Gain Agility

+1 AG

Gain Luck

+1 LK

Harmless

+20 to Steal skill

Here and Now

Gain another level immediately

HtH Evade

If both item slots are empty or contain unarmed-class weapons (spiked knuckles, power fists, etc.),
at the end of a combat round AC increases by 2 per unused AP, plus 1/12 your Unarmed skill
Slots containing non-weapon items or grenades are treated as empty.

Kama Sutra Master

Better sex rating

Karma Beacon

Improves karma modifiers

Light Step

Reduces chance to set off traps

Living Anatomy

+10 to Doctor skill
+5 damage to living critters (all types except robots and aliens)

Magnetic Personality

Can have one more NPC (maximum of 5)

Negotiator

+10 to Speech and Barter skills

Pack Rat

+50 to carry weight

Pyromaniac

+5 damage with fire weapons

Quick Recovery

Only takes 1 AP to stand up

Salesman

+20 to Barter skill

Stonewall

Less likely to be knocked down

Thief

+10 to Sneak, Lockpick, Steal, and Traps skills

Weapon Handling

+3 ST when determining if a weapon can be used properly

Vault City Training

+5 to Doctor and First Aid skills

Alcohol Raised Hit Points

+2 max HP

Alcohol Raised Hit Points II

+4 max HP

Alcohol Lowered Hit Points

-2 max HP

Alcohol Lowered Hit Points II

-4 max HP

Autodoc Raised Hit Points

+2 max HP

Autodoc Raised Hit Points II

+4 max HP

Autodoc Lowered Hit Points

-2 max HP

Autodoc Lowered Hit Points II

-4 max HP

Expert Excrement Expeditor

+5 to Speech skill

Item Perks Edit

These are perks meant to be attached to weapons or armor, and will probably have no effect if given to the player.

Weapon Long Range

Chance to hit increased by (PE-2)*8

Weapon Accurate

Chance to hit increased by 20%

Weapon Penetrate

Reduce DT of armor by 80%

Weapon Knockback

Knocks target back for 1 hex for each 5 points of dealed damage

Weapon Scope Range

Chance to hit increased by (PE-2)*12

Weapon Fast Reload

Reloading takes only 1 AP (instead of 2)

Weapon Night Sight

Removes penalties to chance to hit from the darkness

Weapon Flameboy

More likely to show the most violent death animation for critters killed by fire (reduced to 15 points of damage)

Weapon Enhanced Knockout

All critical hits cause knockout in addition to their regular effects.
Characters with 9 ST have a 1% chance of causing knockout on a regular hit.
Characters with 10 ST have a 2% chance of causing knockout on a regular hit.
Not used by any weapons in the unmodded game.

Powered Armor

+3 ST
+30 Radiation resistance (possible additional effects)

Combat Armor

+20 Radiation resistance (possible additional effects)

Armor Advanced I

+4 ST
+60 Radiation resistance (possible additional effects)

Armor Advanced II

+4 ST
+ 75 Radiation resistance (possible additional effects)

Armor Charisma

+2CH? (not used by any armor)

Damage and combat calculations Edit

ND = net damage value
RD = random damage value produced from weapons hit damage range
RB = ranged bonus (RB=0 unless the player has Bonus Ranged Damage perk)
X = ammo damage multiplier
Y = ammo damage divisor
CM = critical hit damage multiplier (if no critical hit then CM=2, otherwise assigned value from critical hit table)
CD = combat difficulty multiplier (Easy=75, Normal=100, Hard=125)
AI = 1 if critical hit which ignores armor, otherwise 0
ADT = armor damage threshold value
ADR = armor damage resistance value
RM = ammo resistance modifier (only value allowed to be negative or positive in the equation)

Original:
ND = ((RD+RB) × (X/Y) × (CM/2) × (CD/100) - ADT/max(5*AI,1)) × (100 - max((ADR/max(5*AI,1) + RM),0) / 100

ND then rounded to nearest whole number

A hastily written calculator in C:

 #include <stdio.h>
 
 int main (int argc, char **argv)
 {
     float RD = 0, RB = 0, X = 0, Y = 0, CM = 0, CD = 0, ADT = 0, ADR = 0, RM = 0;
 
     printf("Enter parameter in format: >RD RB X Y CM CD ADT ADR RM\n");
     scanf("%f %f %f %f %f %f %f %f %f", &RD, &RB, &X, &Y, &CM, &CD, &ADT, &ADR, &RM);
     printf("Rolled: %f = (50 * %f * (%f/%f) * ((%f + %f)/%f)-%f)*(1-((%f+%f)/100))\n", (((50.0f * CM * (X/Y) * ((RD + RB))/(CD)))-ADT)*(1.0f-((ADR+RM)/100.0f)) , CM, X, Y, RD, RB, CD, ADT, ADR, RM);
 
     return 0;
 }
Examples with some common armor and weapons (assuming no range bonus and no critical hit):
Armors:           
None          N
Leather       LA
Metal         MA
Combat        CA
Power         PA
Adv Power     APA
 
10mm Pistol with 10mm JHP Ammunition
Ammo     X/Y     2/1
Ammo     RM      25
 
        Original Formula
        N     LA     MA     CA     PA     APA
ADT     0     2      4      5      12     15
ADR     0     25     30     40     40     55
----------------------------------------------
5       8     4      3      2      0      0
6       9     5      4      2      0      0
7       11    6      5      3      1      0
8       12    7      5      4      1      0
9       14    8      6      5      2      1
10      15    9      7      5      3      1
11      17    10     8      6      4      1
12      18    11     9      7      4      2
----------------------------------------------

10mm Pistol with 10mm AP Ammunition
Ammo     X/Y     1/2
Ammo     RM      -25
 
        Original Formula
        N     LA     MA     CA     PA     APA
ADT     0     2      4      5      12     15
ADR     0     25     30     40     40     55
----------------------------------------------
5       3     1      0      0      0      0
6       4     1      0      0      0      0
7       4     2      0      0      0      0
8       5     2      0      0      0      0
9       6     3      0      0      0      0
10      6     3      1      0      0      0
11      7     4      1      0      0      0
12      8     4      2      1      0      0
----------------------------------------------

Both melee and hand-to-hand uses the same damage calculation procedure. If you're using a HtH attack, the bonus from the Bonus HtH Damage perk is added to the Melee Damage statistic, while any damage bonuses from the Special Unarmed Attacks (such as Hammer Punch) is added to the initially rolled damage figure (RD in the above formula).


Work in progress.

This is first version of damage calculation in Fallout2:

Dmg_:=Trunc(Dmg_w*(Dmg_mod_1/Dmg_mod_2)-DT_armor)-Trunc(Trunc(Dmg_w*(Dmg_mod_1/Dmg_mod_2)-DT_armor)*(DR_armor+DR_mod_ammo))

here is: Dmg_w - weapon base damage (average from min & max damage) Dmg_mod_1 oraz Dmg_mod_2 - ammo Damage modificators DR_mod_ammo - ammo Damage Resistance (% as 0,01)

DT_armor - armor Damage Treshold DR_armor - armor Damage Resistance (% as 0,01)


Results are truncated by function [trunc] to integer.

Example

Desert Eagle: min_dmg = 10 | | avg_dmg = (10+16)/2= 13 max_dmg = 16 |


JHP ammo: 2/1 20% Dmg_mod_1 = 2 Dmg_mod_2 = 1 DR_mod_ammo = 20% = 0,20


armor Metal Armor: 4/30% DT_armor = 4 DR_armor = 30% = 0,30


Result:

Dmg_:= =Trunc(13*2/1-4)-Trunc(Trunc(13*2/1-4)*(0,30+0,20))=Trunc(26-4)-Trunc(Tunc(26-4)*0,5)=22-Trunc(22*0,5)=22-11=11


For ammo type FMJ: 1/1 -20% result is:

Dmg_:= =Trunc(13*1/1-4)-Trunc(Trunc(13*1/1-4)*(0,30+(-0,20)))=Trunc(13-4)-Trunc(Tunc(13-4)*0,1)=9-Trunc(9*0,1)=9-0=9


So we have such results for Metal Armor:

ammo JHP - 11 dmg ammo AP - 9 dmg

End.


Other description of damage alghoritm in Fallout2:

the formula for calculating damages is:

(((base_damage*dam_mult/dam_div)/2)*cbt_diff_mod)/100-dmg_tresh-(((((base_damage*dam_mult/dam_div)/2)/cbt_diff_mod)/100-dmg_tresh)*ammo_dr_adj)/100

base_damage is a random number in range of weapon damages plus an eventual bonus if you have a bonus for ranged attack and you're using a ranged weapon (the bonus is equal to 2* the level of the perk).

dam_mult is the damages multiplier from the weapon's ammo plus another value passed to the function. This value is almost always 2, I suspect it only changes when you make a critical hit.

dam_div is the damages diviser from the ammo.

cbt_diff_mod is changed by difficulty level: always 100 when the player attacks 75 if playing wimpy 100 if playing normal 125 if playing rough

dmg_tresh is the target'sz damage treshold for the type of damages it concerns.

ammo_dr_adj is the ammo DR adjustement.

Thought it's not definitive, I may have missed something, I'll have to double check.

Some damages can be added after this with the living anatomy perk and the pyromaniac perk.

Around Wikia's network

Random Wiki