Character condition

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

Personal condition
There are many things that can alter your condition. There are different kinds of poison, chems, drugs, wounds that all influence your condition.

Your Character can be:

Or can have crippled limbs like:

If you suffer from multiple crippled limbs you can even become Immobile.

Equipment condition in Fallout 3 and Fallout: New Vegas
The condition of your weapon/armor directly affects its value and damage.

Value
The value of an item is equal to :
 * $$\begin{align}\text{Base value} * \text{Condition}^{1.5}\end{align}$$

For example, the 10mm pistol has a maximum value of 225 Caps when in perfect condition. At 25% condition, the pistol's value is 0.251.5 = 12.5% of its base value, or 28 Caps.

Damage
As condition degrades, weapon damage will scale linearly from full damage at 100% condition to 66% of the damage at 0% condition for firearms.
 * $$\begin{array}{lcl} && DAM(100\% condition;100 skill) \times [0.66 + (0.34 \times Condition\%)] \end{array}$$

This works for single-shot weapons only. For example, the 10mm pistol has a damage rating of 9 at 100% condition and 100 Small Guns. At 25% condition, the pistol's damage would be,
 * $$\begin{array}{lcl} && 9 \times [0.66 + (0.34 \times 0.25)] = 6.705 \approx 7 \end{array}$$

For fully-automatic weapons, the damage will scale linearly to about 54% of the base damage at 0% condition.
 * $$\begin{array}{lcl} && DAM(100\% condition;100 skill) \times [0.54 + (0.46 \times Condition\%)] \end{array}$$

For example, the assault rifle shows an in-game DAM value of 38 at 100% condition and 100 Small Guns. At 25% condition, the assault rifle's displayed damage would be,
 * $$\begin{array}{lcl} && 38 \times [0.54 + (0.46 \times 0.25)] = 24.89 \approx 25 \end{array}$$

Melee weapons scale to 50% damage at 0% condition.
 * $$\begin{array}{lcl} && DAM(100\% condition;100 skill) \times [0.5 + (0.5 \times Condition\%)] \end{array}$$

If the condition of a weapon 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 the weapon, the more likely it is to jam, causing the player to adjust the magazine, thus taking longer to complete the animation. A weapon with 100% CND will never jam, while weapons in a poor state of repair will jam quite frequently.

Armor degradation
Armor's damage resistance is similarly affected - follows a Linear Regression fit to the following formula:[citation needed]
 * $$\begin{array}{lcl} && DR(100\% condition) \times [0.62 + (0.38 \times Condition\%)] \end{array}$$

Weapon degradation
In Fallout 3, the item HP of a weapon is consumed by 3% the base damage of the weapon per shot or attack.

In Fallout: New Vegas, item HP of a weapon degrades at a flat rate of 0.2 item HP per shot or attack when normal rounds (no condition penalty or bonus) are fired. Also due to a bug a weapon can't be repaired to 100% and it'll have about 0.6 to 1 HP less than it's maximum.

Also using some types of ammo and having Raul Tejada as your companion will make a weapon degrade faster or slower.