An ability modifier is a number representing how much an ability score affects the game. Often, this involves adding the modifier to a die roll, such as an attack roll, saving throw, or skill check. A positive modifier is called a bonus, and a negative modifier is called a penalty. The modifier for a given ability is +1 for every 2 points above 10 in that ability score (or -1 for every 2 points below 11). Mathematically, the modifier is (score − 10) / 2, rounded down. For example, an ability score of 14 corresponds to an ability modifier of +2, while a score of 9 corresponds to -1.
An ability modifier cannot be directly modified, only indirectly modified as a result of modifying the corresponding ability score. (Thus the +12 ability cap translates into a cap of +6 for the ability modifier.) When a modifier is indirectly increased by magical means, it is shown in green on the character sheet; when is it decreased, it is shown in red. When a modifier is neither increased nor decreased by magical means, it is shown in white. One major exception to this is the dexterity modifier, as the character sheet will show the dexterity modifier subject to the maximum dexterity bonus, and if this maximum is less than a character's base dexterity modifier, it will be displayed in red (even if no magical decrease is present).
Spellcasters receive bonus spell slots for high casting abilities. As with most in-game effects of abilities, these bonuses are determined by the modifier for the relevant ability: intelligence for wizards; wisdom for clerics, druids, paladins, and rangers; and charisma for sorcerers and bards. In order to receive a bonus spell slot of a given level, the caster must have spell slots of that level by virtue of class level. For this purpose, having "0" spell slots counts (but having "-" spell slots does not).
As a general rule, the number of bonus spell slots of a given level is (modifier − spell level)/4 + 1, rounded down. There are never bonus spell slots for cantrips (level 0 spells).
|Score||Modifier||Bonus spells per day|
|3||-4||can't cast spells tied to this ability|
|4-5||-3||can't cast spells tied to this ability|
|6-7||-2||can't cast spells tied to this ability|
|8-9||-1||can't cast spells tied to this ability|