Repair (Fallout 3)

Repair is a skill $$

Initial level

 * $$\text{Initial level}=2+(2\times\text{Intelligence})+\left\lceil\frac{\text{Luck}}{2}\right\rceil$$

Example: A starting Intelligence of 5 and Luck of 5.
 * $$2+(2\times5)+\left\lceil\frac{5}{2}\right\rceil=15$$

Repair is used to fix damaged equipment (bringing up its condition) by using up a second item identical or similar to the original. Repair also determines the starting condition of custom-made equipment.

Maximum condition
The Repair skill level controls the maximum condition the equipment can be repaired to. This is equal to
 * $$\text{Maximum condition}\%=40\%+\left(0.6\%\times\text{Repair skill}\right)$$

Example: A Repair skill of 50.
 * $$40\%+\left(0.6\%\times50\right)=70\%$$

In other words, every 5 points in Repair raises the maximum condition by 3%. For example, with skill level of 10 allows items to be repaired up to 46%, skill level of 15 allows repair up to 49% and so on. This is important because weapons and armor in poor condition are not as efficient and their value is decreased. Low quality weapons have less accuracy and damage, which reduces effective range and often causes more ammunition to be used to kill enemies when using ranged weapons, or more hits when using melee or unarmed weapons. Ranged weapons in low condition are also more likely to jam, which lengthens the reload animation. Armor in low condition has a lower Damage Resistance (DR) rating. If the condition of a weapon or armor/clothing is completely neglected, the item will break, making the item unusable until it is repaired (armor and clothing will remain on a character after it breaks, but can not be put back on if taken off).

Repair efficiency
Furthermore, repairs become more efficient. The final item condition from repair is equal to:
 * $$\text{RepairedCondition}=5\%+\text{HigherItemCondition}+\left(0.05*\text{LowerItemCondition}\right)+\left(0.15\%*\text{RepairSkill}\right)$$

up to the maximum condition allowed by your repair skill

Example, combining a minigun with a condition of 20% into a minigun with a condition of 10%, by the player character with 10 points in Repair:
 * $$\left(5 + 20 +\left(0.05 * 10\right)+\left(0.15 * 10\right)\right)=27\%$$

The same repair performed by the player character with 50 points in Repair will give:
 * $$\left(5 + 20 +\left(0.05 * 10\right)+\left(0.15 * 50\right)\right)=33\%$$

Other than determining the item type, it does not matter if one repairs item A with item B or the other way around. The formula also works when the two items have different item HP even if one of them is unique — the item condition percentages are taken into account, not HP.

As can be deduced from the formula, the player character's Repair skill is the determining factor, the item used for repairs contributing 5% max to the final state. This can make using or even buying items in good condition for repairs uneconomic. On the other hand, using broken items, which are worthless at 0% condition, is still somewhat effective.

Ways to increase Repair

 * Permanent
 * Leveling up (10+ Intelligence (+3 with the Educated perk))
 * Bobblehead - Repair (+10)
 * Dean's Electronics (+1 or +2 with Comprehension)
 * Gun Nut (+5 with each rank, max 3 ranks)
 * Tag! (+15)
 * Temporary
 * Mentats (+2-10 depending on Intelligence, a perfect Intelligence of 10 will see no benefit.)
 * Vault 101 utility jumpsuit (+5)
 * Dad's wasteland outfit (+5)
 * Repairman jumpsuits, includes Red Racer and Robco (+5)
 * Workman's coveralls (+10) (Point Lookout)

Interactions that require Repair skill

 * 20 Repair is required to disarm microfusion cells wired to a trapped toilet.
 * 23 Repair is needed to disarm bear traps.
 * 30 Repair is necessary to fix the water valves in Megaton during the unmarked quest Treatment.
 * 33 Repair is required to repair the artillery switch in Takoma Industrial if it short circuits after using it a few times.
 * 35 Repair is required in the Anchorage Memorial before, during or after the Wasteland Survival Guide to fix a broken door, if one has the door's component. Without the component, a Repair skill of 95 is required.
 * 40 Repair is needed during Rescue from Paradise to gain an option to free the children.
 * 40 Repair is needed to fix a broken robot during a random encounter. If repaired, the scavenger will give the player character two energy cells. With a Speech check, the player character can convince him to give them 100 caps and the energy cells.
 * 45 Repair is needed to disarm rigged combat shotguns.
 * 60 Repair is needed to disable the turret power generator during Stealing Independence.
 * 75 Repair allows one to repair the elevator to the Statesman Hotel's roof yourself during the quest Reilly's Rangers. Otherwise, a fission battery will be needed.
 * 85 Repair is required to disarm laser tripwire emitters in Raven Rock during The American Dream.
 * 44 Repair is required to shut off the radiation in the Chinese Intelligence bunker.