Critical Hit

Critical Hits are hits which cause extra damage, or other side effects. If a hit is successful, it may become a critical hit if it passes Critical Chance. The effect of the hit is determined by the another roll, on the critical hit table. Effect depends on the area hit, and various unknown variables. The effect of a critical hit can be modified by the Perk Better Criticals.

Note that the chance for a critical hit is determined by Critical Chance, and is not the same as critical effect. See Aimed Shot in the Combat section for more info.

Example
The following example is a bit tricky: you might want to open another window with reference material Situation: Alvin York (S5, P9, E5, C3, I5, A10, L10) is carrying a Hunting Rifle and has a Small Guns skill of 150%, and one of his traits is Finesse. He spies an armored gentleman, wearing Metal Armor some distance (8 hexes) away, and decides to make an aimed shot for the eyes. This is what happens:

Alvin's base to hit is (150 - 30) + (8 * 9) + (No penalty) - (15 + 5) + 4 - 60 = 112%, a definite hit! Alvin's critical chance is (1 * 10) + (10) + (a mysterious number) = Critical hit! Alvin rolls 1d100 for the critical effect table, and gets 85. His damage is (0.7 * 20 * 3) - (armor ignored) = 42

Mr. Metal Man loses 42 of his 70 hp, and staggers around blindly. With his remaining 4 of 10 action points, Alvin advances closer to Mr. Metal Man, who lost his responding turn as a result of the critical.

Alvin fires at the eyes again. BTH is the same, and CC is successful. CE rolls a 95.

Mr Man screams in agony, as a round of ammunition pierces his visor, blinding him. He falls slowly to his knees, bewildered and overcome. Bleeding from his helmet, he keels over, killed by the 56 damage AND the "instant kill" effect. With his remaining 4 action points, Alvin York marries Gracie Williams, has seven children, and dies at the age of 76.

Fallout 3
In Fallout 3, the critical hit feature is simplified from Fallout 1 & 2. When a weapon is fired, it has a predefined, specific percentage chance of getting a critical hit (with a few exceptions, see below), which is essentially just added damage to the original base damage (the damage that will be dealt if the PC does not score a critical hit). This obviously sounds much simpler that that of the first two games, but it is still more complex than it sounds. 