Damage formula

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There isn't a single, general purpose damage formula, but different types of damage have different means of calculating damage.

In general, damage can be calculated as [(Raw Damage) - (Damage Reduction)] * (Chance to hit) over an action's given speed.

Raw Damage[1]

  • Weapon damage: which covers damage calculation for player weapons, unarmed combat, and throwing.
  • Spell damage: Most spells, wands, and monster abilities deal damage in dice notation, and deal nD( (Spellpower * multiplier / divisor) + constant). Spellpower is determined by skill (and for monsters, HD). Each spell has its own multiplier, divisor, and constant. See a spell's own page for more details.
    • If the dice has a non-integer amount of sides, it is often rounded in a weighted manner. That is, 1d1.25 has a 25% chance to be 1d2 and a 75% chance to be 1d1. However, this varies on a case-by-case basis; sometimes dice round down or round to the nearest integer.
    • Certain spells like Shatter may further be multiplied by external factors.
    • By default, spells check AC and EV. Some may ignore one or the other, or both.
  • Poison deals damage over time. The more poison you receive, the more the poison "stacks", and the faster you take damage.
  • Certain effects like Agony, Torment, and flay are percentages of your maximum health.

Damage from monsters is unknown(?), but their maximum damage is displayed on examination.


  1. not to be confused with weapons' base damage

Other Factors

  • To-hit: Determines accuracy (chance to-hit) of an attack. Some attacks can't miss, which is an infinite to-hit.
  • Weapon speed: Determines how fast you swing/fire a weapon or fists. Most spells have a delay of 1.0.

Damage Reduction

  • Resistances reduce damage of a specific type. Player and monster resistances are not symmetrical.
  • Armour class (AC) will reduce most attacks by (0 to AC) damage.
  • Evasion score (EV) determines how likely you are to dodge an avoidable attack completely. See Evasion#To-hit_versus_EV for formulas.
  • Shield score (SH) determines how likely you are to block an attack completely. Melee attacks, ranged attacks, and certain projectile-like spells can be blocked. See Shields#Blocking for formulas