Damage Formula

The battle simulator feature is a decent method for inquiring how much damage one unit will do to another, or which units will win in a certain matchup or arrangement, but for the sake of precisely calculating damage dealt from one stack to another (, the damage formula for a given attack (primary or secondary) is as follows...

Damage Formula

UnitR_Losses = Number_of_UnitA * UnitA_attack_power * accuracy * UnitA_damage_modifier * UnitA_efficiency * (1 - (UnitR_resistance/100)) * UnitR_defensive_abilities / UnitR_hitpoints

• UnitA is the attacking unit
  
• UnitR is the unit receiving the attack
  
• accuracy is Unit A's accuracy in attacking UnitR; base accuracy is 0.3 on defense and regular attacks and 0.2 on sieges, but often modified by Sun favor, unit abilities, enchantments, battle spells, the warlord hero, etc.
  
• UnitA_damage_modifier is typically a random number between 0.2 and 0.8, but the average of 0.5 is usually used
  
• UnitR_Defensive_Abilities would be unit abilities like healing (0.7), scales (0.75), regeneration (0.8), charm (0.5), large shield (0.5), weakness (2.0), etc., which would all be multiplied together
  

Alternatve Version of Damage Formula

Alternatively, this calculation can be broken up into intermediate parts...

Attack = Number_of_UnitA * UnitA_attack_power * accuracy * UnitA_damage_modifier * UnitA_efficiency
Defend = UnitR_hitpoints / (1 - (UnitR_resistance/100))
UnitR_Losses = Attack/Defend

Examples

Regular Attack: 245 Water Elemental attacking Vampire

Vampire_Losses = 245 * 400,000 * 0.2 * 0.5 * 1.0 * 0.15 * 0.5 / 4500 = 163.3 => 163 dead Vampire