Critical hit

A critical hit is when an attack deals three times the normal damage (not to be confused with Weapon effectiveness). A unit's critical hit rate at any given time is most directly influenced by the equipped weapon's "crt" stat. Most weapons raise the chance of scoring a critical hit by only a small amount; however, certain weapons and spells (e.g: Killer Lance, Killing Edge, Killer Axe, and Luna) have a higher chance of landing a critical hit than most weapons. Even then, the critical hit rate is usually around 35 percent, depending on the class and level of the unit wielding the weapon.

In most games in the series, when a critical hit activates, the critical-inducing unit performs a flashy set of movements unique to its class. For the most part, melee weapon units spin their weapons rapidly when performing a critical hit; some sword-wielding classes, such as the Swordmaster (pictured) or Myrmidon, move fast enough to make it appear that they are in more than one place at once and that they disappear momentarily. Magic-using units have a tendency to visibly summon or charge more energy in some ways, such as the Druid tendency to be ringed by their power (pictured). Also, in the 3-D games there are two animations for a critical hit: one for for a killing blow and the other if it simply causes damage. Also, the airbone units have a Critical Hit annimation for battles over the ground and another one when airbone.

Factors

 * Class Critical Bonus: Some promoted classes, notably the Swordmaster and Berserker, have a "class critical bonus", which represents a base critical hit rate a member of the class will almost always have in battle. In Fire Emblem: Radiant Dawn, there were five levels of Class Critical Bonuses (Crit +5, Crit +10, Crit +15, Crit +20, Crit +25), represented as skills permanently attached to the Sniper, Marksman, Reaver, Halberdier, Sentinel, Assassin, Myrmidon, Swordmaster and Trueblade classes.
 * Skills: Some skills increase critical hit rate under certain circumstances. For example, the Wrath skill boosts the critical hit rate when the user's HP is at 1/3 or less.
 * Pursuit Critical Coefficient in Fire Emblem: Thracia 776 a limit is placed on critical rate during the first Double Attack hit and then multiplies it during the second hit.

Critical hit rate calculation
Unit's skill/2 + 5% (If S-rank in Rekka no Ken and The Sacred Stones) + the weapon critical chance + the support bonus (if any) + the class critical bonus (if any) + character's skills (if any) - the enemy's Luck.
 * To calculate a Silencer percent chance of an Assassin, you must halve his Critical Hit percentage (except in Radiant Dawn, where it is half the skill stat).

Hence, it is possible in Fire Emblem: Rekka no Ken for Swordmasters to gain a Critical Hit rate of 100% or more; when it exceeds 100 percent, only the last two digits will be shown.

However, the unit must also be able to hit the opponent first. That is, the hit percentage is taken into consideration before the critical percentage. So if a unit has a low chance to hit, but a very high chance to use a critical, (like from the use of the Gamble skill) the unit may miss altogether.

Critical hits can be completely negated by units carrying the Iron Rune (or the Hoplon Guard or the skill Fortune).