How can you calculate damage?

Question

how does the game add up all the power and defense and attack

Comments

The answer needs to be updated (with working images) because this might have better SEO rankings than other damage calculation questions.

Answer 1

This shows how they do it in generation 5.

Level-This one is self explanatory. The higher your pokemon's level, the stronger the attack.

Attack-This one is also special attack if you're using a special move. If you use a move like swords dance, then those modifications are made beforehand. For instance, if you have a pokemon with 150 attack that uses swords dance, it will go to 300.

Defense-same as attack in that you use special defense for special moves. The number is based on your target's defense.

Base- the Base damage of the attack. For example, Earthquake has a base power of 100.

Modifier is for situational things:

STAB- If your pokemon's move matches its type, it'll be stronger.

type-this is where type matchups come in. If I use a grass move on swampert, it would be for because of his 4X weakness to grass.

critical-If you get a critical hit, then this powers up. This one is luck though.

other-This is for things like helping hand, weather, items, etc.

rand-Every time you attack, a random number ranging from .85 to 1 is selected.

Comments

So each move can strike with different power in gen 5?

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If you are referring to the 'random' modifier, then yes, that's what it means. Moves don't do a set amount of damage. The formula has also remained unchanged since, and so still applies today.

Answer 2

The easiest way to calculate damage is by using a damage calculator. It's by far the most efficient and fastest way to get damage outputs from every Pokémon.

Besides the calculator, a simple mathematical expression can be used to calculate total damage. This would be a rough figure and for an exact value, using a damage calculator is preferred.

Source

• Level is the level of the attacking Pokémon.
• A is the effective Attack stat of the attacking Pokémon if the used move is physical, or the effective Special Attack stat of the attacking Pokémon if the used move is special (ignoring negative stat stages for a critical hit).
• D is the effective Defense stat of the target if the used move is a physical move or a special move that uses the target's Defense stat, or the effective Special Defense of the target if the used move is another special move (ignoring positive stat stages for a critical hit).
• Power is the effective power of the used move.
• Targets are 0.75 (0.5 in Battle Royals) if the move has more than one target when the move is executed, and 1 otherwise.
• PB is 0.25 (0.5 in Generation VI) if the move is the second strike of Parental Bond, and 1 otherwise.
• Weather is 1.5 if a Water-type move is being used during rain or a Fire-type move during harsh sunlight, 0.5 if a Water-type move is used during harsh sunlight or a Fire-type move during rain, and 1 otherwise or if any Pokémon on the field have the Ability Cloud Nine or Air Lock.
• Critical is 1.5 (2 in Generation V) for a critical hit, and 1 otherwise. Decimals are rounded down to the nearest integer. It is always 1 if the target's Ability is Battle Armor or Shell Armor or if the target is under the effect of Lucky Chant.
• random is a random factor. Namely, it is recognized as a multiplication from a random integer between 85 and 100, inclusive, then divided by 100. Decimals are rounded down to the nearest integer.

note: random belongs to [0.85, 1.00]. The output would be a decimal multiplied by 0.85 and 1.00 both, and the definite damage would be an integral value between them. This depends on luck.

• STAB is the same-type attack bonus. This is equal to 1.5 if the move's type matches any of the user's types, 2 if the user of the move additionally has Adaptability, and 1 otherwise or if the attacker and/or used move is typeless. If the used move is a combination Pledge move, STAB is always 1.5 (or 2 if the user's Ability is Adaptability).
• Type is the type effectiveness. This can be 0.125, 0.25, 0.5 (not very effective); 1 (normally effective); 2, 4, or 8 (super effective), depending on both the move's and target's types. The 0.125 and 8 can potentially be obtained on a Pokémon under the effect of Forest's Curse or Trick-or-Treat. If the used move is Struggle or typeless Revelation Dance, or the target is typeless, Type is always 1. Decimals are rounded down to the nearest integer.
• Burn is 0.5 if the attacker is burned, its Ability is not Guts, and the used move is physical (other than Facade from Generation VI onward), and 1 otherwise.
• other is 1 in most cases, and a different multiplier when specific interactions of moves, Abilities, or items take effect.
• ZMove is 0.25 if the move is a Z-Move, Max Move, or G-Max Move being used into a protection move (Protect, Detect, King's Shield, Spiky Shield, Mat Block, Baneful Bunker, or Obstruct), the move is Clangorous Soulblaze being used into Wide Guard, or the move is a Z-Move, Max Move, or G-Max Move given priority by Prankster or Gale Wings being used into Quick Guard, and 1 otherwise.

Comments

It's probably worth mentioning that https://www.trainertower.com/dawoblefets-damage-dissertation/ includes much more detail about rounding and damage modifiers than the Bulbapedia article does.