Damage

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 an elemental type, its effectiveness is largely determined by the targetted Pokémon's type. Moves can have regular effectiveness or be super effective, not very effective, or not effective at all.

Super effective

When a move is super effective, it inflicts double the damage it would normally do. For example, a move like Megahorn used against a Template:Type2 Pokémon will be super effective because Template:Type2 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 Template:Type2 move like Surf will be damaged four times as much by the move as a Template:Type2 Pokémon would be, because both Rock and Ground Pokémon are weak to Water moves.

Not very effective

When a move is not very effective, 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 Template:Type2 move. Likewise, a Normal/Flying Pokémon hit by a Template:Type2 move will be damaged normally, as the super-effectiveness of Fighting against Normal is canceled out by the not-very-effectiveness of Fighting against Flying.

Not effective

When a move is not effective, it does not damage the Pokémon at all and that Pokémon is "immune" to that type. This immunity includes status moves of that type. For example, the Template:Type2 move Thunderbolt will have no affect on a Template:Type2 Pokémon such as Garchomp. Likewise, using the move Thunder Wave will prove useless and yields a "It does not affect Garchomp" (whereas a Confuse Ray that simply missed yields "It did not affect Garchomp"). Certain types are immune to specific moves, such as Template:Type2 Pokémon being immune to Leech Seed.

Critical hit

A move will sometimes inflict a critical hit against another Pokémon. This will double the damage done after type effectiveness calculations occur, leading to the possibility of a doubly-super effective move that gets a critical hit to do eight times as much damage as normal. Pokémon with the Sniper ability will triple the damage done during a critical hit rather than double it. Regular moves have a 6.25% chance of scoring a critical hit, but some moves have increased critical hit rates.

The chance of causing a critical hit can be modified by using moves or items that increase the critical hit level.

Level	Percentage	Moves
1	6.25%	Regular moves
2	12.5%	Moves with an increased critical hit rate: Slash, Stone Edge etc.
3	25%	Moves used by Farfetch'd and Chansey with the Stick and Lucky Punch attached, respectively
4	33.3%	Critical hit moves used in combination with Super Luck
5	50%	Critical hit moves used in combination with Super Luck and a Razor Claw or Scope Lens.

Scope Lens and Razor Claw add 1 level each, the Stick adds 2 levels (for Farfetch'd only), the Lucky Punch adds 2 levels (for Chansey only), Focus Energy adds a level, Super Luck doubles the amount of levels and goes before the items are calculated in. 50% is the maximum critical hit ratio, since no situation exceeds it.

When a move scores a critical hit, damage is calculated based on either the modified or unmodified attack and defense stats, whichever is more advantageous to the attacker. For example, an attacker who has used Swords Dance and then makes a critical hit will get the benefit of the increased Attack, while one affected by Charm will use its normal Attack score. Another example would be if a team had Light Screen or Reflect on it and the attacker scored a critical on the team with the certain wall; the defense added by the wall would then be ignored, and will do double normal damage. In Generation I, critical hits always ignore stat modifiers, even if this is disadvantageous to the attacker.

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 Template:Type2 move used by a Fire-type Pokémon. Dual-typed 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.

Weather

Main article: Weather conditions

Template:Type2 and Template:Type2 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.

Abilities

Main article: Abilities

Abilities come in a wide variety, and have various effects on damage modification. These affects 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:

• Blaze, Overgrow, Torrent and Swarm increase the power of Template:Type2, Template:Type2, Template:Type2 and Template:Type2 moves by 50% when the user's HP falls below 33%, respectively.
• Thick Fat decreases the power of the opponents' Fire-type and Ice-type moves by 50%. Heatproof decreases the power of opponents' Fire-type moves by 50%.
• Levitate provides immunity to Template:Type2 moves, and Soundproof provides immunity to sound-based moves.
• Volt Absorb and Water Absorb grant immunity to Template:Type2 and Template:Type2 moves respectively, healing the user's HP by 25% instead.
• Dry Skin works in part like Water Absorb, healing when hit with a Template:Type2 move, but it also heals the Pokémon slightly during rain. However, it also causes the Pokémon to receive additional damage from Template:Type2 attacks and receive slight damage during sunshine.
• Flash Fire negates the effect of opponents' Fire-type moves and instead increases the power of the ability's user's own Fire-type attacks. Similarly, Motor Drive negates the effect of opponents' Electric-type moves and instead causes the ability's user's Speed to increase. These abilities include status moves like Will-O-Wisp and Thunder Wave.
• Mold Breaker removes all ability-based immunities to the user's moves.
• Scrappy removes Template:Type2 Pokémon's immunity to the Template:Type2 and Template:Type2 moves of the user.
• Drizzle, Drought, Sand Stream and Snow Warning all cause different weather conditions.
• Adaptability doubles the power of moves of the same type as the user.
• Hustle boosts the power of the user's moves by 50%.
• Pure Power and Huge Power both double the power of the user's physical attacks.
• Technician increases the power of the user's moves with base power 60 or less by 50%.
• Super Luck increases the user's critical hit ratio.
• Battle Armor and Shell Armor block critical hits.
• Sniper increases the power of the user's critical hits.
• Tinted Lens doubles the power of the user's moves that are not very effective.
• Solid Rock and Filter each reduce the power of super effective moves on the ability's user by one third.
• Wonder Guard reduces the power of the opponent's attacks that are not super effective to zero.

Items

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:

• Muscle Band boosts physical moves by 10%
• Wise Glasses boost special moves by 10%
• Expert Belt boosts super-effective attacks by 20%
• Life Orb boosts all attacks by 30%
• Metronome boosts the power of moves used repeatedly

Other

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 have a 75% modifier.
• 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 between 0.85× and 1.00×. The probability of each percentage is nonuniform due to integer division rounding, causing an approximately 6% chance for each point between 0.85 and 0.99, but only a 2.5% chance for the full damage.