A lot of people have been asking about damage calcs and formulas and how certain abilities and moves apply to damage. Here are all your answers.

[CODE]Damage = (((((((Level × 2 ÷ 5) + 2) × BasePower × [Sp]Atk ÷ 50) ÷ [Sp]Def) × Mod1) + 2)
× CH × Mod2 × R ÷ 100) × STAB × Type1 × Type2 × Mod3[/CODE]


You can simplify all this very easily, assuming lvl 100 battles (no babies lawl).

[CODE]Damage = (((42 × BasePower × [Sp]Atk ÷ 50 ÷ [Sp]Def × Mod1) + 2) × CH × Mod2 × R ÷ 100)
× STAB × Type1 × Type2 × Mod3[/CODE]

The way Smogon presents all this data is great. However there is a lot to consider, and a lot to take in to understand it fully.

Here's a list of Base Power and Attack Stat modifiers that apply to the damage formula. They only effect the "BasePower" and "[Sp]Atk" values of the formula.

Base Power Modifiers
Items:
Muscle Band - 1.1 BP multiplier for Physical Attacks
Wise Glasses - 1.1 BP multiplier for Special Attacks
Type Boosters (includes plates and incense) - 1.2 BP multiplier for Attacks of the type which the plate or incense applies to
Adamant Orb - 1.2 BP multiplier for Dragon and Steel type Attacks, if and only if the user is Dialga
Lustrous Orb[i] - 1.2 BP multiplier for Dragon and Water type Attacks, if and only if the user is Palkia

Abilities
User Abilities
[i]Rivalry - 1.25 BP multiplier if the user is the same gender as the targeted Pokemon, 0.75 BP multiplier if the user is the opposite gender as the targeted Pokemon, no change if the targeted Pokemon is genderless
Reckless - 1.2 BP multiplier if the user is using a recoil move
Iron Fist - 1.2 BP multiplier if the user is using a punching move
Blaze - 1.5 BP multiplier if the user uses a Fire move and its current HP is less than 1/3 of its maximum HP (rounded down)
Overgrow - 1.5 BP multiplier if the user uses a Grass move and its current HP is less than 1/3 of its maximum HP (rounded down)
Torrent - 1.5 BP multiplier if the user uses a Water move and its current HP is less than 1/3 of its maximum HP (rounded down)
Swarm - 1.5 BP multiplier if the user uses a Bug move and its current HP is less than 1/3 of its maximum HP (rounded down)
Technician - 1.5 BP multiplier if the user uses a move with BP less than or equal to 60

Foe Abilities
Thick Fat - 0.5 BP multiplier if the Foe is using a Fire or Ice type move
Heatproof - 0.5 BP multiplier if the Foe is using a Fire type move
Dry Skin - 1.25 BP multiplier if the Foe is using a Fire type move



Attack (or Special) Stat Modifiers
Items:
Choice Band - 1.5 Attack Stat multiplier if held
Choice Specs - 1.5 Special Attack Stat multiplier if held
Light Ball - 2 Attack and Special Attack Stat multiplier if held by Pikachu
Thick Club - 2 Attack Stat multiplier if held by Cubone or Marowak
Soul Dew - 1.5 Special Attack Stat multiplier if held by Latios or Latias
Deepseatooth - 2 Special Attack Stat multiplier if held by Clamperl

Abilities:
Pure Power - 2 Attack Stat multiplier
Huge Power - 2 Attack Stat multiplier
Flower Gift - 1.5 Attack and Special Attack Stat multiplier
Guts - 1.5 Attack Stat multiplier
Hustle - 1.5 Attack Stat multiplier (and physical moves have 80% accuracy)
Slow Start - 0.5 Attack Stat multiplier if the user has been in battle for less than 5 turns, no change otherwise
Plus - 1.5 Special Attack Stat multiplier if doubles partner has Minus ability
Minus - 1.5 Special Attack Stat multiplier if doubles partner has Plus ability
Solar Power - 1.5 Special Attack Stat multiplier if Sunny Day is in effect (at cost of 1/8 maximum HP per turn)


So now that we all have an understanding of what effects the Base Power and Attacking stats when it comes to abilities and items, we can also add in stat modifying moves.

Stat Modifiers
There are lots of different stat modifiers in this game, but they all follow the same principle in application with the damage formula.

[CODE]Stat Modifier is -6: SM = 2/8 (0.25)
Stat Modifier is -5: SM = 2/7 (0.2857)
Stat Modifier is -4: SM = 2/6 (0.3333)
Stat Modifier is -3: SM = 2/5 (0.4)
Stat Modifier is -2: SM = 2/4 (0.5)
Stat Modifier is -1: SM = 2/3 (0.6667)
Stat Modifier is 0: SM = 2/2 (1)
Stat Modifier is 1: SM = 3/2 (1.5)
Stat Modifier is 2: SM = 4/2 (2)
Stat Modifier is 3: SM = 5/2 (2.5)
Stat Modifier is 4: SM = 6/2 (3)
Stat Modifier is 5: SM = 7/2 (3.5)
Stat Modifier is 6: SM = 8/2 (4)[/CODE]

All Stat Modifiers follow the same principle. The following moves apply, with appropriate increases and decreases listed (please note, only move that apply to attack and/or defense stats are listed, there are more).

Attack
Meditate (+1)
Howl (+1)
Dragon Dance (+1 Atk and Speed)
Swords Dance (+2)
Accupressure (+2, random stat)
Curse (+1 Atk and Def, -1 Speed)
Growl (-1)
Charm (-2)
Featherdance (-2)
Intimidate (-1, ability, only on switch in)
Swagger (+2, applies to foe, induces confusion)

Defense
Harden (+1)
Defense Curl (+1)
Acid Armor (+2)
Barrier (+2)
Iron Defense (+2)




EDIT: Ugh, need some help with the html tables here. Or am I supposed to use BBCode list tags?

Here's the link to the Smogon Damage Formula until I'm able to get that table fixed and finish this: http://www.smogon.com/forums/showthread.php?t=25175