Damage calculation

Damage Types
There are several different types of damage in Guild Wars.
 * Elemental damage
 * Fire damage
 * Cold damage
 * Lightning damage
 * Earth damage
 * Physical damage
 * Blunt damage
 * Piercing damage
 * Slashing damage
 * Other damage:
 * Holy damage
 * Light damage
 * Shadow damage
 * Dark damage
 * Chaos damage

Health Degeneration also causes loss of hit points, but isn't considered damage by the game engine.

Damage Calculation
First of all, if the attack is blocked or evaded, then the target takes no damage.

Assuming the attack was not blocked or evaded, we first calculate the effective armor level (EAL) the target has against that attack. Note that this value can vary greatly depending on the attack. At one extreme are attacks that "ignore armor" – they impart the full damage regardless of armor or armor bonuses. Examples include any attack that deals shadow damage, or offensive spells such as Obsidian Flame. Most attacks, however, are resisted by some form of armor.

Every piece of armor worn by a character has a specific base armor level (BAL). The maximum BAL of spellcasters is generally 60 (Droknar's Armor or later), and rangers and warriors have armor with higher BAL. To the base AL we add any AL that is specific to the type of damage. Many warrior armors have armor bonus versus physical damage; all ranger armors have bonuses versus elemental damage; and elementalist armor sets have bonuses versus specific kinds of elemental damage. Weapons and shields can also yield AL bonuses. Finally, enchantments such as Weaken Armor and skills such as Healing Signet add AL penalties, which are treated as negative bonuses. We thus obtain the net armor level (NAL).


 * NAL = BAL + AL bonuses - AL penalties

Next, we have to account for any armor penetration present in the attack. Lightning damage and certain kinds of holy damage, for instance, have a set amount of penetration (usually 20%). The warrior attribute Strength increases armor penetration of melee attacks. Weapons can also give armor penetration bonuses. Add up all the various bits of armor penetration to obtain the net armor penetration (NAP). We can now calculate the effective armor level (EAL):


 * EAL = NAL &times; (1 - NAP/100)

The EAL is the amount of resistance that any particular attack receives. The game treats an EAL of 60 as "normal" against a level 20 spell or a 12-attribute melee/bow attack: all damage values indicated in skill descriptions assume an EAL of 60 versus that level 20 spell or 12-attribute melee/bow attack. This damage value is called the base damage (BD) of the attack. If the EAL is more than 60, then the actual damage dealt will be less than the BD; dually, an EAL of less than 60 gives an actual damage of more than the BD. Certain skills that add damage "before armor" add to this base damage; these are added together to give the damage bonus (DB).

We are now ready to calculate the net damage (ND):


 * ND = (BD + DB) &times; 2(60 - EAL)/40

Net damage is not always the effective damage dealt to the target. Certain weapons or enchantments like Judge's Insight offer a damage bonus that is added to the ND. Damage reduction. caused by Weakness for example, reduces net damage by melee by 66%. Certain shields and warrior armors have further damage reduction which is simply subtracted from the ND. With these final modifications taken into account, we get the effctive damage (ED) dealt to the target.

Of course, enchantments like Protective Spirit or Protective Bond might prevent the entire effective damage from actually manifesting on the target.

Effect of Attribute Ranks
The melee attributes Marksmanship, Hammer Mastery, Axe Mastery and Swordsmanship alter the net damage equation somewhat -- the 60 in the exponent is replaced by a multiple of the attribute rank (AR) corresponding to your melee weapon. Precisely, the equation is:


 * ND = (BD + DB) &times; 2(5 &times; AR - EAL)/40

Note that every 8 ranks in an attribute doubles the net damage. In fact, every rank in a melee attribute scales the damage by exactly a factor of 2(1/8), or an increase of roughly 9%. Note that the effect of cumulative ranks is compounded: 5 ranks don't give a 45% damage increase but (1.095 - 1) &times; 100 &asymp; 53% increase.

Weapons differ from spells in having not a single BD value but a range of possible values. At the time of attack, a specific BD value is selected uniformly from the damage range of the weapon.

Effect of Character Levels
Warning: This subsection of the article should be taken as mostly speculative.

Unlike melee attacks, spells always see the full 60 in the exponent of the ND equation. However, there is an added damage bonus if the attacker is of a higher level than the target (or a damage reduction if the reverse). Precisely, for every 13 levels of difference the net damage output is doubled (or halved), giving the equation:


 * ND = (BD + DB) &times; 2(60 - EAL)/40 + (AtL - TgL)/13

(where AtL and TgL are the attacker and target levels respectively).

Illustrative Examples
[examples and graphs to be added presently]

Damage Groups
It is useful to classify damage into damage groups (especially for PvP).
 * Spike Damage
 * Damage Over Time