Critical Chance

Critical Chance is a derived statistic in Fallout, Fallout 2, Fallout 3, Fallout: New Vegas, Fallout Tactics and Fallout: Brotherhood of Steel.

Fallout, Fallout 2 and Fallout Tactics
An Aimed Shot has a higher chance to score a critical hit than an unaimed shot. In Fallout Tactics, the Science skill also apparently has an effect on critical chance against robotic enemies.
 * $$\text{Initial level}=\text{Luck}\times1\%$$


 * The Finesse trait increases the critical chance by 10%.
 * The More Criticals perk increases the critical chance by 5% per rank.
 * The Sniper perk increases the critical chance to 10*Luck for ranged weapons.
 * The Slayer perk increases the critical chance to 100% for melee weapons.

Base Chance
Luck is the main base factor that determines the chances of a critical strike on an opponent.
 * $$\text{Initial level}=\text{Luck}\times1\%$$

Example: A starting Luck of 5.
 * $$5~(\text{Luck}) \times 1\%=5\%~(\text{Base chance})$$

Notes:
 * Maximum initial base is capped at 10%.
 * Ninja perk can increase this limit by another +15% for Melee and Unarmed weapons.
 * Finesse perk can increase this limit by another +5%.
 * Survival Expert perk can increase this limit by another +3%.
 * Strikes dealt in V.A.T.S have additional +15% critical chance added.
 * Some weapons have 0% chance of a critical strike (see Critical Multiplier for detail of effects).

You can also check your critical chance with the console command.

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.
 * $$\text{Base chance}\times\text{Critical multiplier}$$

Example: A starting Luck of 5 and using a sniper rifle, which has a x5 Critical Multiplier.
 * $$5\%~(\text{Base chance})\times5~(\text{Critical multiplier})=25\%~(\text{Critical chance})$$

Notes
 * The critical multiplier for fully-automatic weapons is much lower than for single-shot weapons.
 * There are a few weapons that have a x0 multiplier, making it impossible to score a critical hit.
 * For a detailed list of weapon critical multipliers, see here.

Weapon Condition
The final critical chance is also modified by weapon condition.
 * $$\mbox{Critical chance} \times \mbox{Condition}$$

For example, a character with 5 Luck and using a sniper rifle in 50% condition would have,
 * $$25\%~(\text{Critical chance})\times\frac{50}{100}~(\text{Condition})=12.5\%~\text{Critical chance}$$

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.


 * Attributes, perks and traits that increase critical chance include:
 * Luck (permanent +1-10%)
 * Built to Destroy (permanent +3%)
 * Light Touch¹ (temporary +5% while wearing any light armor)(Dead Money)
 * Finesse (permanent +5%)
 * Ninja² (permanent +15% for melee and unarmed weapons)
 * Laser Commander¹ (permanent +10% with lasers).
 * Set Lasers for Fun¹ (permanent +2/4% with energy weapons)
 * Meat of Champions (+1 Luck for 60 seconds after eating a fresh corpse)
 * Intense Training (permanent +1 Luck if selected)
 * Luck Implant (permanent +1 Luck if purchased)
 * ¹ The critical chance added by these perks is a flat bonus and is not affected by your weapon's critical multiplier.
 * ² Ninja multiplies your total critical chance after all modifiers by 1.15; thus it adds 15% of your normal critical chance, not a flat 15% boost.


 * Items that increase critical chance:
 * 1st Recon beret (+5%)
 * Naughty nightwear (+1 Luck, effective +1%)
 * True Police Stories (temporary +5% (+10% with Comprehension))
 * Vault-Tec Assisted Targeting System¹ (temporary +5% critical hit chance when using V.A.T.S.)
 * Lucky shades (+1 Luck, effective +1%)
 * Armor of the 87th Tribe (+3%)(Lonesome Road)
 * Elite riot gear (+5%)(Lonesome Road)
 * Ulysses' duster (+5%)(Lonesome Road)
 * Joshua Graham's armor (+3%) (Honest Hearts)
 * Salt-Upon-Wounds' helmet (+2%) (Honest Hearts)
 * Marked beast face helmet (+2%) (Lonesome Road)
 * ¹ The critical chance added by V.A.T.S. is a flat bonus and is not affected by your weapon's critical multiplier.

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 The Slugger 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 Butcher skill (only Cain) increases the critical chance by 5% only for blades for each ranks until a total of 25%.
 * The Desert Soldier skill (only female character) increases the critical chance by 5% only for conventional weapons (weapon that uses 9mm) for each ranks until a total of 25%.
 * The Future Woman skill (only female character) increases the critical chance by 5% only for energy weapons for each ranks until a total of 25%.
 * The Heavy Hitter skill (only human male character) increases the critical chance by 5% only for Blunt weapon (Gloves, Clubs and Hammers) for each ranks until a total of 25%.
 * The Pyromaniac skill (only Cain) increases the critical chance by 5% when using a fire-based weapon (like the frag grenade, flamer, etc.) for each ranks until a total of 25%.
 * The Slayer skill increases the critical chance by 5% for each ranks until a total of 25%.
 * The Wastelander skill (only human male character) increases the critical chance by 10% only when using home-made weapons for each ranks until a total of 50%.

The type of weapon with a maximum critical chance with the skill required is the home-made weapons with a total of 75%.

Gallery
Szansa na trafienie krytyczne Шанс на критическое попадание