Advantage

For a comprehensive summary of the mechanics behind all rolls and modifiers, see: Die Rolls

Advantage and Disadvantage are a gameplay mechanic that can greatly affect the success of dice rolls. They can apply to Attack Rolls, Saving Throws, and Ability Checks, but not to Damage Rolls.

Advantage

When you roll with Advantage, you perform the roll twice, and use the higher result. It doesn't stack beyond 2 dice, regardless of how many sources of advantages you have.

Example: You roll two  d20 for an Attack Roll, the results are 16 and 4. Your effective result is 16.

Advantage and Disadvantage cancels each other, and having multiple sources doesn't change this either. Even if you have three sources of Advantage, a single source of Disadvantage will cancel it. [Needs confirmation, because it is the same text like in Disadvantage]

Examples of situations that grant Advantage on attack rolls:

• Attacking an enemy that is under these conditions: Restrained, Prone, Sleeping, Entangled, Paralysed, Off balance, Enwebbed, Blinded.
• Attacking an enemy while being Hidden or invisible.
• Armor, Weapons, and Spells that grant advantage when attacking enemies of a specific Race.

Disadvantage

When you roll with Disadvantage, you perform the roll twice, and use the lower result. It doesn't stack beyond 2 dice, regardless of how many sources of disadvantages you have.

Example: You roll two  d20 for an Attack Roll, because you have Disadvantage. The results are 16 and 4. Your effective result is 4.

Disadvantage and Advantage cancel each other, and having multiple sources doesn't change this either. Even if you have three sources of Disadvantage, a single source of advantage will cancel it. [Needs confirmation, because it is the same text like in Disadvantage]

Examples of situations that grant Disadvantage on attack rolls:

• Trying to make a ranged attack against an enemy that is within 5ft and making you Threatened.
• Trying to attack an enemy Obscured by Darkness.
• Various spells and abilities that grant Disadvantage.

External Links

• The unexpected logic behind rolling multiple dice and picking the highest by Matt Parker