Characters and monsters are good at various things. Some are skilled with many weapons, while others can only use a few. Some are better at understanding people's motives, and others are better at unlocking the secrets of the multiverse. All creatures have a [[Proficiency Bonus]], which reflects the impact that training has on the creature's capabilities. A character's [[Proficiency Bonus]] increases as the character gains levels. A monster's [[Proficiency Bonus]] is based on its [[Challenge Rating]]. The [[Proficiency Bonus Table]] shows how the bonus is determined. This bonus is applied to a [[D20 Test]] when the creature has [[Proficiency]] in a [[Skills|Skill]], in a [[Saving Throw]], or with an item that the creature uses to make the [[D20 Test]]. The bonus is also used for [[Spell Attacks]] and for calculating the DC of [[Saving Throws]] for [[Spells]]. > [!ERROR] The Bonus Doesn't Stack > Your [[Proficiency Bonus]] can't be added to a die roll or another number more than once. Occasionally, a [[Proficiency Bonus]] might be multiplied or divided (doubled or halved) before being added. For example, the [[Expertise]] feature doubles the [[Proficiency Bonus]] for certain ability checks. Whenever the bonus is used, it can be multiplied only once and divided only once.