Character condition

Condition can refer to two things — either the condition of the character or (in Fallout 3, Fallout: New Vegas, and Fallout 76) the condition of their equipment.

Character condition
The most common character conditions found in Fallout 3, Fallout: New Vegas, and Fallout 4 are poisons from Chems or from the environment, and damage from combat. Fallout 4 is currently the only one in the Fallout series to include illnesses.

Poisoned

 * Addicted
 * Drunk
 * Overdose
 * Poisoned
 * Radiated
 * Withdrawal

Other

 * Encumbered
 * Well Rested

Illness
In Fallout 4, the Sole Survivor can become ill in Survival mode.

All illness can be cured with antibiotics, being well rested for several days, or by any doctor. Specific illnesses can be prevented by taking the appropriate herbal remedy prior to the disease check.

Untreated Illness (if not fatal) generally persists for around a week of rest (well fed, hydrated and rested). However, there is a chance it will persist for an additional week.

Illness chance in general is increased by all forms of Fatigue but does not directly impact Action Points. Regardless of risk exposures, the bed slept in and the duration of sleep, there is always a slight chance of contracting an illness when going to sleep (but announced upon waking); sleeping for short periods of time (to save the game, for example) increases this chance overall, due to an increased number of (shorter) sleep sessions, although all sleep sessions after the first will be at the minimum probability, assuming no further risk disease exposures between sleeps.

Checks
An immediate check for contracting a disease is made 30 real time seconds after a high risk exposure. A check is also made when going to sleep. Apart from these two situations, risk exposure simply increases the probability (disease risk pool) of getting a disease at the next check. Checks are not "rolled for" unless the chance is 25%+.

All checks resulting in a new disease, clear the risk pool down to its minimum value (which depends on current Fatigue level). All checks that don't produce a new disease cause a small drain down of the risk pool. All checks upon sleeping also clear the risk pool down to the minimum, after the check.

Risk factors
In addition to poor sleep quality, causes of disease risk include: using chems, eating anything (but especially bad or uncooked meat), drinking or swimming in irradiated water, being in rain, drinking Nuka-Cola and taking damage from feral ghouls, bugs or other infected creatures. Each event puts the player character at increased risk of contracting an illness. High risk events trigger a near immediate disease check. Even if a single event doesn't trigger an illness to start, each event will increase the probability of contracting an illness with each event, up until the character sleeps (when the final check is made and the disease risk pool is cleared) or gets a new disease (which also clears down the risk pool).

List of diseases

 * Fatigue - Require more frequent sleep to avoid debuffs.
 * Infection - Periodic damage. Similar to Severely Dehydrated and Starving.
 * Insomnia - Sleep provides half as much reduction in tiredness.
 * Lethargy - 50% slower AP regeneration.
 * Parasites - Must eat x2 as much food to avoid hunger or to eliminate any given hunger level.
 * Weakness - Take +20% more damage.

Herbal remedies
Various herbal remedies become available for crafting, purchase and as a loot in Survival mode:
 * Herbal stimulant
 * Herbal antimicrobial
 * Herbal anodyne

Each type of remedy will act (one time only per dose) to prevent one of the two specific diseases that it prevents against, but only if the herbal remedy is taken before the disease check. This means taking the herbal remedy prior to sleeping, or within 30 seconds (real time) of a high risk event.

Equipment condition
Note that any equations are not to be taken as literal representations of what happens in-game, but as accurate, general representations of the logic.

The condition of a weapon or armor directly affects its value and damage for weapon or Damage Threshold for armor, respectively.

If the condition of an item degrades all the way to 0%, the item is broken and cannot be used until repaired. In the case of equipped armor and clothing, bonuses to skills or attributes will still apply even if the item is broken, but once removed it will have to be repaired before it can be re-equipped.

Another consequence of poor condition when using weapons is the reload animation. The lower the condition of a weapon, the more likely it is to jam, causing the player to adjust the magazine, thus taking longer to complete the animation. A weapon at 100% condition (or at least 75% in New Vegas) will never jam, while weapons in a poor state of repair will jam quite frequently.

Value
The value of an item is calculated by :
 * $$\text{Value} = \text{Base value} \times \text{Condition} ^ {1.5}$$


 * Condition is a number ranging from 0 to 1.

Also, knowing the current value of an item it is possible to find the condition:
 * $$\text{Condition} = \left(\frac{\text{Value}}{\text{Base value}}\right)^\frac{2}{3}$$

For example, the 10mm pistol has a maximum value of 225 caps when in perfect condition. At 50% (or 0.5) condition, the pistol's value is 225 * (0.5 ^ 1.5) = 225 * 0.3535, or 35.3% of its base value (225): 79 caps.

Damage
As condition degrades, non-melee weapon damage will scale linearly from full damage at 100% condition to roughly two-thirds damage at 0% condition for single-shot ranged weapons and roughly half damage for fully-automatic ranged weapons and melee weapons.

\text{Dam}_{\text{Skill}=100}= \text{Base} \times (\text{Minimum} + \text{Condition} \times (1 - \text{Minimum})) $$
 * Condition is a number ranging from 0 to 1.
 * Minimum is .66 for single-shot weapons, .54 for fully-automatic weapons, .5 for melee weapons.

For example, the 10mm pistol has a base damage of 9. At 25% condition and 100 Guns, the pistol's damage would be:
 * $$\text{Dam}_{\text{Guns}=100}=9 \times (.66 + .25 \times .34) = 6.705 \approx 7$$

In another example example, the assault rifle has a base damage of 38. At 25% condition and 100 Guns, the assault rifle's displayed damage would be:
 * $$\text{Dam}_{\text{Guns}=100}=38 \times (.54 + .25 \times .46) = 24.89 \approx 25$$

Armor protection
Armor's damage resistance and Damage Threshold are similarly affected, though skill is not necessary and the value for Minimum is .62:
 * $$\text{DR or DT}=\text{Base} \times (.62 + \text{Condition} \times .38)$$

Equipment degradation
All equipable items in Fallout 3 and Fallout: New Vegas have item health, which helps determine how quickly an item condition degrades from use and from being hit in combat. At full item health, an item is in 100% condition. Similarly, at close to 0 item health, an item is about to break. In Fallout 3, item health decreases per use by a percentage of the base damage of the weapon.
 * Small Guns degrade at 3% of base weapon damage per shot.
 * Energy Weapons degrade at 4% of base weapon damage per shot.
 * Unarmed and Melee Weapons degrade at 5% of base weapon damage per attack.
 * Big Guns degrade at 6% of base weapon damage per shot.

For example, the Plasma rifle has a base damage of 45 and an item health of 900. Each shot will decay the health by 1.8 health, which means that it takes 500 shots to take this plasma rifle from full condition to broken.

Damage
As condition degrades, weapon damage will scale linearly from full damage at 75% condition to half the damage at 0% condition.

\text{Dam}_{\text{Skill}=100}= \text{Base} \times \left(   0.5 + \min      \left( \frac{0.5\times \text{Condition}}{0.75}, 0.5 \right) \right) $$

Armor protection
As condition degrades, armor protection will scale linearly from full protection at 50% condition to about 2/3 of full protection at 0% condition.

\text{DR or DT}=\text{Base} \times \left(   0.66 + \min \left( \frac{0.34\times \text{Condition}}{0.5}, 0.34 \right) \right) $$

Equipment degradation
Weapon condition degrades at a flat rate of 0.2 item health per shot. V.A.T.S. does not impose an additional penalty, but various types of ammunition can increase or decrease the degradation rate (indicated by a "CND x 1.5" or similar in the Pip-Boy 3000, which means a 1.5 multiplier for decay). Having Raul Tejada as a companion can make a weapon degrade slower (a .5 multiplier for Regular Maintenance, a .25 multiplier for Full Maintenance).

Armor condition degrades if an incoming attack power exceeds DT of the armor.