Critical Chance Critical Chance is a derived statistic in " Fallout " , " Fallout 2 " , " Fallout 3 " , " " , " " and " " . " Fallout " , " Fallout 2 " and " Fallout Tactics " . An Aimed Shot has a critical chance bonus equal to the chance - to - hit penalty of the targeted body part . In " Fallout Tactics " , the Science skill also has an effect on critical chance against robotic enemies . The Chance to Hit adds a slight bonus to critical chance if the attack hits the intended target . The formula used to determine whether an attack hits or misses is ( Chance to Hit ) - ( RandomNumberBetween1and100 ) . If the remainder is 0 or more , the attack is a hit . If it ' s negative , the attack is a miss . If the attack hits its target , the same random number that was subtracted from the chance to hit is used to calculate the critical chance bonus of the successful hit . This bonus is equal to ( ChanceToHit - RandomNumberBetween1and100 ) / 10 rounded down . Thus if a successful attack ' s chance to hit was 49 % , this critical chance bonus could be anything between 0 % ( random number is between 40 and 49 ) and 4 % ( random number is between 1 and 9 ) . A successful hit whose chance to hit was 95 % has a critical chance bonus ranging from 0 % to 9 % . The average critical chance bonus of a successful hit with a 95 % hit chance is ( 5x9 + 10x8 + 10x7 + 10x6 + 10x5 + 10x4 + 10x3 + 10x2 + 10x1 + 10x0 ) / 95 = 4 . 26 % " Fallout 3 " . Base Chance . Luck is the main base factor that determines the chances of a critical strike on an opponent . Example : A starting Luck of 5 . Notes : Critical Multiplier . All weapons have a critical multiplier that modifies the player character ' s base critical hit chance . This may improve or hinder the ability to score a critical hit depending on the weapon ' s Critical multiplier . Example : A starting Luck of 5 and using a sniper rifle , which has a x5 Critical Multiplier . Notes Weapon Condition . The final critical chance is also modified by weapon condition . For example , a character with 5 Luck and using a sniper rifle in 50 % condition would have , " Fallout : New Vegas " . The formulas for critical chance seem unchanged from Fallout 3 . You receive 1 % of critical chance for each point placed into Luck . During character creation , you can add an additional 3 % for all weapons by choosing the Built to Destroy trait . Currently , the highest possible critical chance that will be affected by your multiplier is 38 % ( 10 Luck , Finesse , Built to Destroy , 1st Recon Beret , Elite riot gear / Ulysses ' Duster , True Police Stories with Comprehension ) . As mentioned above , Light Touch , Laser Commander , Set Lasers for Fun , Ninja , and V . A . T . S . can further increase your chance . " Fallout : Brotherhood of Steel " . In Fallout : Brotherhood of Steel , a critical hit allows to exceed the maximum limit of damage for a weapon . Some weapons are very powerful with a high critical chance , such as the double - barrel shotgun or and also the weapons in bursts . An energy weapon with the skill Energy Charge or a Melee weapon with the skill Special Attack can be extremely powerful if the charged attack is a critical hit . The chance to cause a critical hit in combat is increased by Initial Level : Each character starts with a 1 % critical chance . The type of weapon with a maximum critical chance with the skill required is the home - made weapons with a total of 75 % .