Damage calculation

Damage in Guild Wars results from actions taken by attackers that subtract a portion of a defender's health. This definition includes many attacks or skills (including spells) but does not include health degeneration, life stealing, sacrifice, or health reduction caused by skills such as Infuse Health or Illusion of Weakness.

When an attacker attempts to damage a target, the following is factored in:
 * The damage type, such as Fire or Blunt. The amount of damage done may vary due to the defender's armor and resistances to that specific damage type.
 * The attacker's ability to inflict the damage.
 * The target's ability to resist this damage.
 * Bonuses on both sides. An attacker may have bonuses that augment the damage and the target may have bonuses that reduce the damage.

A Simplified Damage Calculation
''Note: For simplicity, on this page the term attack describes any attempt to damage an opponent. However, whenever the word "attack" is used in skill descriptions, it refers to the attack action.''

There are many different factors to consider while calculating damage. To avoid confusion, this section presents a simplified damage calculation which only takes into consideration the more common factors.

The Approximate Damage (ApproxD) depends on the Raw Damage (RD) and the Armor Effect (AE).
 * '''ApproxD = RD &times; AE;

For damage that ignore armor, AE is set to 1.

Raw Damage
Skill-based offense (like Shock) have a specific raw damage (RD) value indicated in the skill description.

Weapons attacks select RD each time uniformly from the damage range of the weapon. For weapons that have an attribute requirement on their damage range, there is actually another hidden range used for when the attacker does not meet the requirement (see here for details).

Effective Damage
The Effective Damage (ED) considers all the Damage Modifiers that were dropped when calculating the Approximate Damage. The ED depends on the Raw Damage (RD), various Damage Modifiers (D*), and the Armor Effect (AE).


 * ED = [([RD &times; DScale &times; AE] + DShift) &times; DMult] + DNeg

Again, for attacks that ignore armor, AE is set to 1, essentially removing it from the equation.

Damage Cap and Redirection
Certain enchantments will restrict the maximum damage the target can receive, or redirect some of the damage away from the target, thus making the received damage less than the Effective Damage. Redirection is always applied before the cap.

A Simple Example
You are a Warrior, with 16 Swordmastery and weilding a Vampiric Longsword of Fortitude, attacking a Monk, who has 70 armour (either from Blessed Insignia or Stalwart Insignia), with a normal attack.

Raw Damage
The minimum Raw Damage is 15 and the maximum is 22. (Life steal is not considered damage by the game and doesn't count.)

Damage Rating
Using the second formula,
 * DRnoncaster = 5 &times; Rank;  if Rank <= Threshold
 * DRnoncaster = 5 &times; Threshold + 2 &times; (Rank-Threshold);  if Rank > Threshold
 * Threshold1 = Level /2 + 2

Your rank in Swordmastery exceeds the threshold (which is 12 for a level 20 character), so your Damage Rating is DRnoncaster = 5 &times; Threshold + 2 &times; (Rank-Threshold) = 5 &times; 12 + 2 &times; 4 = 68

Armor Rating
The monks BaseAR is 60 - standard caster armour.

She is using Stalwart (or Blessed) Insignia, but she is not using any +armour mods on her weapon, so her ARShift is +10. You have no armour penetration.

Her Armour Rating is EffAR = BaseAR &times; (1 - NAP) + ARShift = 60 + 10 = 70

Using the formula for Armour Effect, AE = 2(EffDR - EffAR)/40 = 2(68 - 70)/40 = 2(-2)/40 

Using a calculator (or the chart), gives an Armour Effect of 96%. Which takes us all the way back to the first equation. Your Approximate Damage is (15-22) &times; 96% = (14 - 21). Not very spectacular, but it's the process that is important.

An Unnecessarily Complicated Example
You are a Warrior, with 16 Axe Mastery and 10 Strength this time and wielding a Sundering Chaos Axe of Fortitude, attacking a Monk, who has 70 armour and is under the effect of Dark Escape. Your first attack is Executioner's Strike, followed by Critical Chop.


 * ED = [([RD &times; DScale &times; AE] + DShift) &times; DMult] + DNeg

Armour Effect
As before, you have a Damage Rating of 68 (at level 20 and 16 weapon mastery), but the Armour Rating has changed, due to armour penetration. Your Sundering prefix does not trigger.

The new Armour Rating is EffAR = BaseAR &times; (1 - NAP) + ARShift = 60 &times; (1 - 0.10) + 10 = 64

Which gives a total Armour Effect of 107%.

Damage Scale
Your axe does +15% from its inscription and +20% damage from customisation, for a total Damage Scale of 35%.

Damage Shifter
You have no external damage bonus other than your attack skill, like Strength of Honour or Order of Pain, so the Damage Shifter is +42.

Damage Multiplier
Dark Escape gives the monk a Damage Multiplier of 1/2.

Damage Negator
None

Effective Damage
The new raw damage for your axe is 6-28, giving a final formula of ED = [([RD &times; DScale &times; AE] + DShift) &times; DMult] + DNeg

The minimum damage is ED = [([6 &times; 1.35 &times; 1.07] + 42) &times; 0.5] + 0 = 25

The maximum damage is ED = [([28 &times; 1.35 &times; 1.07] + 42) &times; 0.5] + 0 = 41

Related Articles

 * Spike damage
 * Damage over time
 * Point Blank Area of Effect
 * Area of Effect

Original References
The present article is built on the results of the research laid out in the original unannotated version of the following article, with additional original research conducted by users of the GuildWiki.
 * SonOfRah's damage article