Radiation resistance
Radiation resistance  
 
The amount of radiation you are exposed to is reduced by this percentage. Radiation Resistance can be modified by the type of armor worn, and antiradiation chems.
”— Fallout Ingame descriptionRadiation resistance is a derived statistic in Fallout, Fallout 2, Fallout 3, Fallout Tactics, Fallout: New Vegas, Fallout 4, and Fallout 76.
It reduces radiation damage by a percentage.
RadX temporarily increases Radiation Resistance.
Contents
Fallout, Fallout 2, Fallout Tactics, Fallout: New Vegas
Notes:
 Average characters will have a 10% radiation resistance.
 The Fast Metabolism trait sets initial radiation resistance to 0.
 The Rad Resistance perk increases radiation resistance by 15% per rank. (10% per rank in FO1)
 The Vault City Inoculations perk increases radiation resistance by 10%.
 RadX temporarily increases radiation resistance by 50%. Half of it is lost after 24 hours, with resistance returning to its original value after another 24 hours.
 In Fallout, rad resistance can go as high as 100% (Which is needed to survive The Glow). In Fallout 2, it is capped at 95%, in Fallout: New Vegas, however, it is capped at 85%.
Fallout 3
Example: A starting Endurance of 5.
Permanently increasing Radiation Resistance
 The Cyborg perk gives +10% Radiation Resistance.
 The Rad Resistance perk gives +25% Radiation resistance.
 The Survival Expert perk gives between +2% and +6% Radiation resistance.
 The Pitt Fighter perk from The Pitt gives +3% Radiation Resistance.
 The Booster Shot perk from The Pitt gives +10% Radiation Resistance.
Temporarily increasing Radiation Resistance
 The RadX drug gives up to +75% Radiation resistance with the Medicine skill at 100.
 An advanced radiation suit, the environment suit, Lesko's lab coat, Filtration helmet, a radiation suit and the modified utility jumpsuit will all increase Radiation Resistance while worn.
 All power armor has some Radiation Resistance.
Notes:
 In Fallout 3 rad resistance is capped at 85%.
Fallout 4 and Fallout 76
Damage resistance in both of the Creation Engine games is essentially the same and uses three separate armor types for the three available damage types:
 DamageResist, used to determine resistance against ballistic or normal weapons  most conventional firearms, melee, and unarmed weapons, as well as creature attacks,
 EnergyResist, used against weapons dealing energy damage,
 RadiationResist, used against  what else?  radiationbased weapons.
To determine the damage reduction, the game first checks the following:
 If target has 0 Armor = 0% DamageReduction
 If Armor < 15% AttackDamage = 1% Damage Reduction
 If Armor > 550x Attack Damage = 95% Damage Reduction
Otherwise, it performs the following calculation: ^{[1]}
 DamageReduction = 10.5*(AttackDamage / DamageResist)^0.3653
At extreme values, Energy damage can be nullified, but Ballistic or Normal damage will only be reduced by a max of 95%.
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