Shane is an avid TTRPG player and DM for 7+ years, on top of being a writer. I love all things D&D and am always up to try a new system!
What Is Passive Perception?
Passive perception is an excellent mechanic in 5th edition D&D that basically determines how much a player character notices without having to make a roll or be specifically looking for something.
Mechanically, this is done to keep the game moving along so players aren't making non-stop rolls to try to notice things that they really should be able to notice without issue.
This is also a good way to reward players in-game who have invested a lot into their Wisdom ability score and perception stat in particular. For characters who aren't big magic slingers or battle tanks, being able to spot an ambush ahead of time or spot something out of place to investigate an important bit of evidence allows non-combat-heavy builds to thrive.
Let's dive deeper into passive perception, how it works, and when to use it versus active perception checks or investigation in your next D&D game.
How to Calculate Passive Perception
Figuring out passive perception scores for characters is actually really simple. There is a basic formula and then some additional considerations.
For characters proficient in perception the formula is:
10 + Wisdom Ability Score Modifier + Proficiency Bonus (if proficient)
So for a level 10 rogue with a 16 Wisdom score the passive perception would be 17. 10 + 3 for wisdom modifier + 4 for proficiency bonus.
For a player who is not proficient in perception the formula is:
10 + Wisdom Ability Score Modifier
This is also referred to as the Passive Wisdom score for all players.
The player's passive perception should, as long as there aren't any extenuating circumstances, allow them to notice anything that they would see with an active perception check up to that number.
So if there was someone taking a special interest in the party in a semi-crowded market, and the difficulty is set at a 16, the earlier rogue with the 17 passive perception score would notice immediately even if the rest of the party did not.
Passive Perception vs. Perception Check vs. Investigation
Some of the confusion about passive perception can be traced back to the fact that perception and investigation have a lot of overlap, which can be confusing in and of itself.
That also causes even more confusing separating passive perception from active perception from investigation.
So how to handle this?
The DM makes the call on a case by case basis. Generally, as long as the game master is consistent, it's not a problem. In some cases, if the player thoroughly knows how passive perception works will be relied on the DM to make the call.
So what are the general rules of thumb that explain when to use each skill? Keeping in mind there is overlap, the way I remember it is:
- Perception applies to details you notice about your environment
- Passive perception is how many of the details in your environment you see without actively trying
- Investigation is when you are actively searching - taking a specific action
Passive perception means your always observant rogue walks into the library and notices that many books on one particular book shelf appear more uniform in size and shape than any other shelf in the room.
A perception check after noticing this oddity reveals something isn't quite right about the shape and appearance of the books that make up that shelf.
An investigation check happens when the rogue actually studies the book shelf closely looking for a secret passage, hidden safe, or any other cause for why things look off.
When Does Passive Perception Not Apply?
Generally speaking, when a game uses passive perception that is used as the general baseline. In other words, if a character has a passive perception of 15 and they roll a 5, they still observe at a 15.
The DM also has a lot of leeway in deciding when passive perception applies and when to alter it. If the group is rushing through a fierce storm, they might be distracted and take a perception check at a disadvantage or a penalty.
Same if they are trying to notice something going on nearby while in the middle of a battle.
However, most of the time passive perception can be an important part of the process and a great way to keep the game moving while using narrative to reward players invested in perception (Example: "There are many dangerous traps in the dungeon but your rogue's 22 passive perception allows you to easily spot them and work around them with relatively little delay.").
The DM also has the right to call for a specific perception check when they think a detail may or may not set off potential alarm bells or interest in a specific situation.
Example 1: Walking Into a Study
The party walks into a private study in the long abandoned house. Party members prepare to investigate various items in the room, but they stop to see what they can perceive.
The barbarian has a passive perception of 11. He notices it is a room with books. There are plenty of cobwebs and dust.
The wizard has a passive perception of 14 sees the age of the room but also notes a particularly large tome on the desk that seems to have less dust on it than other parts of the room.
The ranger has a passive perception of 17. She notes the dust, the cobwebs, the large tome that maybe the wizard should look at. There's something about the room that just seems off, and the ranger can't help but to think a more thorough investigation of this room is necessary.
The monk's passive perception of 22 allows him to take in many details their companions miss. The room appears old, but there are scuffs indicating some very light foot steps, a pattern to broken webs, and something slightly tilting the desk tome up, indicating the tome as a trap.
They warn the others and suggest searching for a very well hidden secret door.
Example 2: Walking into a Dungeon Ambush
The barbarian moves at the head of the party, prepared for any danger ahead when the ranger hisses "Stop!" Pointing out a trip wire and discolored stone plate on the ground.
They had been warned the bandits' cave was trapped but these early traps indicated this mission might be even more dangerous than the party originally expected.
"You still have that magic hand spell?" the monk asks the wizard.
Using the over 20 passive perception from a lifetime of training, the monk points to holes in the wall barely visible in the shadows ahead, as well as old blood stains in the hall indicating a trap neither he nor the ranger had picked up on.
Alternative Dungeon Example (to Reward Party & Speed Up Game)
Your party moves cautiously into the labyrinth. While it is heavily trapped, thanks to the high perception of your ranger and monk, your group manages to identify a dozen traps, avoid setting them off, and still make good time, moving to the deeper level of the caverns in about half an hour.
Example 3: Politics in the King's Court
Bards were not only expert performers from Josiah's homeland, but they were outstanding spies, as well.
Using long learned lessons that honed his perception over the years, they came in handy for the group as a passive perception of 24 meant even as he performed admirably for the court, he also noticed:
- The page sneaking into side rooms where he didn't belong
- The shared glances between a king's advisor and the visiting congregation's general
- The suspiciously stealthy and smooth movements of a cloaked figure moving closer and closer to the front where the most important figures were seated
The bard reaches out to his party members using his telepathic bonds, giving them a chance to intercept dangers they had no chance of even knowing about without the bard's sharp eyes.
Passive Perception Is a Great In-Game Mechanic
Passive perception might be an optional mechanic that DMs can choose to use in a 5th Edition game, but it's an excellent one that works wonders once the game master and players all understand how it works.
Passive perception can:
- Speed up the game
- Reward players who invest heavily in perception
- Paint the feeling of being strong capable heroes in campaign
- Render most traps and ambushes obsolete
When used well, passive perception is a huge net positive to a 5E campaign in many ways, and is an optional rule that every DM should embrace.
© 2022 Shane Dayton