# Fallout engine calculations

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## 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 of1. * Note that this value is added to themaximum possible damageof 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 least1.

**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.~~