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Damage modification

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Damage modification is a system of multipliers used to change the damage dealt in a battle. These modifiers affect how the damage is calculated by multiplying the move's base power in various ways. These modifiers range from doubling to halving and even negating the damage done.

Type effectiveness

Since each move has a type, its effectiveness is largely determined by the targeted Pokémon's type. Moves can have regular effectiveness or be super effective, not very effective, or not effective at all. The effectiveness of types against one another has varied among generations, see this page.

Super effective

"Super effective" redirects here. For the webcomic, see Super Effective (webcomic).

"It's super effective" redirects here. For the podcast, see It's Super Effective (podcast).

"Weakness" redirects here. For the TCG mechanic, see Glossary (TCG) → Weakness.

When a move is super effective, it inflicts double the damage it would normally do. For example, a move like Megahorn used against a Psychic type Pokémon will be super effective because Bug-type moves are super effective against Psychic types. This effect can stack up; for example, a Pokémon that is Rock/Ground and is hit by a Water-type move like Surf will be damaged four times as much by the move as a Normal-type Pokémon would be, because both Rock and Ground Pokémon are weak to Water moves.

Not very effective

"Resistance" redirects here. For the TCG mechanic, see Glossary (TCG) → Resistance.

When a move is not very effective, or resistant, it deals half of the damage it would normally do. This works exactly like super effective moves, and can stack up. For example, a Steel/Rock Pokémon will be damaged by a quarter of the amount by a Normal-type move. Likewise, a Normal/Flying Pokémon hit by a Fighting-type move will be damaged normally, as Normal's weakness to Fighting is canceled out by Flying's resistance to it.

Not effective

When a move is not effective, it does not damage the Pokémon at all and that Pokémon is "immune" to all attacks of that type; the move will yield a message of "It doesn't affect the Pokémon..." Certain types are also immune to specific status moves, such as Ground-type Pokémon being immune to the Electric-type Thunder Wave, or Grass-type Pokémon being immune to Leech Seed as well as powder and spore moves.

Critical hit

Main article: Critical hit

A move will sometimes inflict a critical hit against another Pokémon. This will increase the damage done by 1.5× (2× prior to Generation VI) prior to type effectiveness calculations.

Same-type attack bonus

Main article: Same-type attack bonus

A move used by a Pokémon that is of the same type as the move itself will do 150% of its normal damage, such as a Fire-type move used by a Fire-type Pokémon. Dual-type Pokémon will receive this bonus for both of their types, and a Pokémon whose type can change in-battle will receive the bonus for whatever type they are when they make the move. Pokémon with Adaptability have this increased to 200% (an effective boost of ~33.3%).


Main article: Weather conditions

Water-type and Fire-type moves' damage will be modified by rain and sunshine. If Rain Dance causes a downpour, Water-type moves will do 50% more damage and Fire-type moves will do 50% less damage. If Sunny Day causes harsh sunlight, Fire-type moves will do 50% more damage and Water-type moves will do 50% less damage.


Main article: Ability

Abilities come in a wide variety, and have various effects on damage modification. These effects range from increasing and decreasing the power of moves of a specific type, granting immunities, and even changing the power of moves affected by other damage modifiers. These Abilities include:


See also: Type-enhancing item

Some held items increase the power of an attack by a small percentage. Most of these items boost attacks only of a certain type by 20%. Some items can also modify damage by boosting the attacker's offensive stats or the victim's defensive stats. Some Berries also weaken an opponent's super-effective move.

Other held items that modify damage include:


A number of other variables can affect the amount of damage caused by an attack.

  • If the attacker is burned and their Ability is not Guts, their physical damage will be decreased by half.
  • In a Double Battle, moves that hit multiple targets do 75% of the damage they do in one-on-one battles.
  • Reflect and Light Screen decrease opponents' physical and special attacks, respectively, by 50% in a one-on-one battle and 33% in a Double Battle.

Randomization adjustment

Every time a regular attack is executed, the actual damage caused is adjusted by a random multiplier - an integer percentage between 85% and 100%.

In Generations I and II, the random modifier does not have uniform probability for all percentages between 85 and 100. This is because the computer will generate a random number from 217 to 255 (217 is about 85.10% of 255), multiply it by 100, and then divide it by 255, to get the random number from 85 to 100 that the computer will divide by 100 to get the final adjustment.

As a result, the odd numbers from 85 to 89 and the even numbers from 90 to 98 have a 7.69% (3 in 39) probability of being chosen, while the even numbers from 86 to 88 and the odd numbers from 91 to 99 have a 5.13% (2 in 39) probability of being chosen. The number 100, the least probable number, has a mere 2.56% (1 in 39) chance of being chosen.

In all subsequent games, the random adjustment is determined by generating a 4 bit number (0 through 15). The computer then subtracts it from 100, and then divides the result by 100 to get the final adjustment. This results in the same integer percentage between 85% and 100%, with an even distribution of occurrence.


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