UPDATE AND TL;DR: as it was pointed out in the comments, according to RAW advantage/disadvantage adds or subtracts 5 from the ability roll accordingly. But that is not really fair and the reason for +-5 rule seems to be for ease of remembering. +-4 is more statistically accurate and represents true average rolls at advantage/disadvantage.
Hey!
Let's preface with some DnD maths.
It is a well-known fact that the average "at least 10" roll has a probability of 55% (100% for 1, 95% for 2 etc) In other words, 10 DC is beaten in about half the times on average, considering +0 modifier.
According to the statistical breakdown of effect advantage/disadvantage does on rolls (which can be researched online -- for example, here) DC 6 can be beaten with 56.3% probability at disadvantage and DC 14 can be beaten with 57.8% probability at advantage.
Since 5e is "roll the remainder down" system, exactly those numbers were chosen, but you can move them to DC 7 and DC 15 at disadvantage and advantage respectively if you feel it would be more fair.
Now to the interesting part -- what situations can lead to actually applying this math?
Well, that's the DM's discretion, but one notable example would be a drow character. As you probably know, a drow has a disadvantage on perception checks that rely on sight when the object of such check or the drow themselves are under direct sunlight. This is a more-or-less permanent mechanical condition and not just modified once by a spell or some feature.
So, in my campaign we use this ruling which is not stated anywhere in the official sources, but I feel goes very much in accordance with mechanical feel. Any drow in a situation stated as above has a passive perception score of 6 + modifier, when relying on sight.
For instance, if someone is trying to hide from sight in a town at noon, it would be a hard time for a drow standing right on the street under sunlight to find hiding creature. This is just one, but straightforward example of such ruling. When using an advantage/disadvantage that is imposed on just the next roll, this is to DM discretion. While a character has such an advantage/disadvantage on next roll it might mean that until they spend it they have a buff/debuff to a passive check, however, this is broken most of the time. Come up with a very good reason if you want to do this!
I am sure you can find more examples in your campaign where adding this gives players more flavor and strengths/weaknesses to play with!
A passive check is a special kind of ability check that doesn't involve any die rolls. Such a check can represent the average result for a task done repeatedly, such as searching for secret doors over and over again, or can be used when the DM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster.
Here's how to determine a character's total for a passive check:
10 + all modifiers that normally apply to the check
If the character has advantage on the check, add 5. For disadvantage, subtract 5. The game refers to a passive check total as a score.
For example, if a 1st-level character has a Wisdom of 15 and proficiency in Perception, he or she has a passive Wisdom (Perception) score of 14. The rules on hiding in the “Dexterity” section below rely on passive checks, as do the exploration rules.
Click ✨ HERE ✨ For My Youtube Videos featuring Guides, Tips & Tricks for using D&D Beyond. Need help with Homebrew? Check out ✨ thisFAQ/Guide thread ✨ by IamSposta.
Yes, I was already pointed out to this rule I missed on reddit. Did not originally find anything on this on Advantage/Disadvantage chapter of PHB and Running the game chapter of DMG.
However, to me it seems it is purely for ease of remembering and actually nerfs players at disadvantage more than on roll -- and buffs players at advantage more, accordingly.
A passive check is a special kind of ability check that doesn't involve any die rolls. Such a check can represent the average result for a task done repeatedly, such as searching for secret doors over and over again, or can be used when the DM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster.
Here's how to determine a character's total for a passive check:
10 + all modifiers that normally apply to the check
If the character has advantage on the check, add 5. For disadvantage, subtract 5. The game refers to a passive check total as a score.
For example, if a 1st-level character has a Wisdom of 15 and proficiency in Perception, he or she has a passive Wisdom (Perception) score of 14. The rules on hiding in the “Dexterity” section below rely on passive checks, as do the exploration rules.
Just a question for my own clarification; it says a character with Wisdom 15 and proficiency in Perception has a passive Wisdom (Perception) score of 14.
If that character has advantage, does one add 5 to the 14 for a score of 19, or does the advantage override everything else and just sets the score to 15?
it's +5 to the passive perception so that would make the 14 become 19.
Rollback Post to RevisionRollBack
Click ✨ HERE ✨ For My Youtube Videos featuring Guides, Tips & Tricks for using D&D Beyond. Need help with Homebrew? Check out ✨ thisFAQ/Guide thread ✨ by IamSposta.
UPDATE AND TL;DR: as it was pointed out in the comments, according to RAW advantage/disadvantage adds or subtracts 5 from the ability roll accordingly. But that is not really fair and the reason for +-5 rule seems to be for ease of remembering. +-4 is more statistically accurate and represents true average rolls at advantage/disadvantage.
Hey!
Let's preface with some DnD maths.
It is a well-known fact that the average "at least 10" roll has a probability of 55% (100% for 1, 95% for 2 etc)
In other words, 10 DC is beaten in about half the times on average, considering +0 modifier.
According to the statistical breakdown of effect advantage/disadvantage does on rolls (which can be researched online -- for example, here) DC 6 can be beaten with 56.3% probability at disadvantage and DC 14 can be beaten with 57.8% probability at advantage.
Since 5e is "roll the remainder down" system, exactly those numbers were chosen, but you can move them to DC 7 and DC 15 at disadvantage and advantage respectively if you feel it would be more fair.
Now to the interesting part -- what situations can lead to actually applying this math?
Well, that's the DM's discretion, but one notable example would be a drow character.
As you probably know, a drow has a disadvantage on perception checks that rely on sight when the object of such check or the drow themselves are under direct sunlight.
This is a more-or-less permanent mechanical condition and not just modified once by a spell or some feature.
So, in my campaign we use this ruling which is not stated anywhere in the official sources, but I feel goes very much in accordance with mechanical feel. Any drow in a situation stated as above has a passive perception score of 6 + modifier, when relying on sight.
For instance, if someone is trying to hide from sight in a town at noon, it would be a hard time for a drow standing right on the street under sunlight to find hiding creature. This is just one, but straightforward example of such ruling. When using an advantage/disadvantage that is imposed on just the next roll, this is to DM discretion. While a character has such an advantage/disadvantage on next roll it might mean that until they spend it they have a buff/debuff to a passive check, however, this is broken most of the time. Come up with a very good reason if you want to do this!
I am sure you can find more examples in your campaign where adding this gives players more flavor and strengths/weaknesses to play with!
Cheers!
I prefer official rules. advantage: +5 to passive check, disadvantage -5 to passive check. Nice, easy, simple and also RAW.
Chapter 7 : Using Ability Scores >> Ability Checks >> Passive Checks
Click ✨ HERE ✨ For My Youtube Videos featuring Guides, Tips & Tricks for using D&D Beyond.
Need help with Homebrew? Check out ✨ this FAQ/Guide thread ✨ by IamSposta.
Yes, I was already pointed out to this rule I missed on reddit. Did not originally find anything on this on Advantage/Disadvantage chapter of PHB and Running the game chapter of DMG.
However, to me it seems it is purely for ease of remembering and actually nerfs players at disadvantage more than on roll -- and buffs players at advantage more, accordingly.
I updated the OP to reflect this.
Just a question for my own clarification; it says a character with Wisdom 15 and proficiency in Perception has a passive Wisdom (Perception) score of 14.
If that character has advantage, does one add 5 to the 14 for a score of 19, or does the advantage override everything else and just sets the score to 15?
it's +5 to the passive perception so that would make the 14 become 19.
Click ✨ HERE ✨ For My Youtube Videos featuring Guides, Tips & Tricks for using D&D Beyond.
Need help with Homebrew? Check out ✨ this FAQ/Guide thread ✨ by IamSposta.
Thank you!