- This article is about the overall bonus to the attack roll; for the item property, see Attack bonus (item property).
The attack bonus (AB) is a number added to a roll of a d20 whenever a creature makes an attack. This total is then compared to the target's armor class to see if the attack hits hard enough to deal damage (before things like damage reductionare considered). The attack bonus is the sum of the base attack bonus, an ability modifier, a bonus subject to the +20 attack bonus cap, modifiers from feats (excluding feats that must be "cast"), and several miscellaneous modifiers.
base attack bonus + ability modifier + capped bonus + feats + miscellaneous
In melee combat, the strength modifier is used, unless the attacker has weapon finesse and a higher dexteritymodifier than strength. In that case, the dexterity modifier is used. In ranged combat, the dexterity modifier is used, unless the attacker has zen archery and a higher wisdom modifier than dexterity. In that case, the wisdom modifier is used.
The bonus subject to the +20 cap includes the higher of the used weapon's attack or enhancement bonus, plus bonuses from spells and spell-like abilities. These bonuses stack when they come from different spells. In this context, "spell-like abilities" includes most feats that must be activated/cast (e.g. bard song). Feats that are toggled (e.g. expertise), situational (e.g. bane of enemies), always on (e.g. epic prowess), or active for a single attack (e.g. disarm) generally do not contribute to the +20 cap, but instead stack with no limit.
Miscellaneous modifiers automatically apply when their conditions are met. These are often overlooked by players since most (all except the mounted penalty) are not included on the character sheet. The various miscellaneous modifiers are as follows.
- Both melee and ranged
- Attacker's size modifier. -2 to +2 AB
- Attacker is invisible or target is blind. +2AB (unless negated by the target's blind fighting)
- Target cannot be seen (hidden, invisible, or out of visual range). -4AB
- Target is flanked. +2AB (unless negated by the target's defensive awareness)
- Target is stunned. +2AB
The bonus for invisible attackers does not apply if the attacker can see through its own type of invisibility (a bug). Being out of visual range typically only applies to non-player characters making ranged attacks in response to being attacked (since players cannot target creatures outside their characters' visual range).
- Melee only
- Target is prone. +4AB
- Ranged only
- Attacker is mounted. -4AB (or -2AB with mounted archery)
- Target is moving. -2AB
- Target is prone. -4AB
- Target is within 3.5 meters of the attacker. -4AB (unless negated by point blank shot)
The mounted penalty only applies in modules that are designed with horses in mind and that have specifically turned on this penalty. This particular penalty is unusual in that it does contribute to the net +20 cap, unlike other situational modifiers.
Decreasing AB
The following spells can be used to directly decrease an enemy's attack bonus: bane, battletide, Bigby's interposing hand, flare, and prayer.
The following (class-specific) feats can be used to temporarily directly decrease an enemy's attack bonus: curse song.
Increasing AB
The following combat feats can be used to directly increase the attack bonus for a single attack (none subject to the cap): disarm(if using a larger weapon), smite evil, and smite good.
The following spells can be used to temporarily directly increase their targets' attack bonus (all subject to the +20 cap): aid, awaken, battletide, blade thirst, bless, bless weapon, divine favor, divine power, greater magic fang, greater magic weapon, holy sword, magic fang, magic weapon, prayer, true strike, and war cry.
The following (class-specific) feats can be used to temporarily directly increase their targets' attack bonus (all subject to the +20 cap): bard song, divine wrath, oath of wrath, rallying cry, and war domain.
The following general feats directly increase attack bonus (none subject to the cap): bane of enemies(ranger class only), epic prowess, epic weapon focus, point blank shot(ranged combat only), and weapon focus.
The following class and racial feats directly increase attack bonus (none subject to the cap): battle training vs. goblins, battle training vs. orcs, battle training vs. reptilians, enchant arrow, epic superior weapon focus, good aim, nature sense, opportunist, and superior weapon focus.
Custom Content Notes
NPCs can reach much higher attack bonus than player characters. However maximum value possible is 127, after this value the attack bonus is rollovered to negative starting with -128 up to zero again. While the combat log shows negative values, the actual hit seems to count with the correct value as if they were positive.