[RPG] How does the math work for Perception checks


Please forgive me, it's been over 40+ years since I've played D&D and just now trying to reboot the changes. Can someone briefly explain Perception check math?

Assume I'm a 5 year old or an idiot, whichever comes first in your mind.

If a character has a Wisdom of 10 and the DM says "roll a Perception check"…
The character then rolls a 1d20 with the hopes of what number? Higher than or lower than 10? Or is it a number only the DM knows about the area/monster/etc.?

Follow-up question:
If a character has a high Wisdom, wouldn't the P.C. be easier to achieve? Assuming a lower roll is easier than a higher roll (yes?).

Best Answer

You may wish to refer to the introductory sections of the PHB, also contained in the freely available Basic Rules, which describe the core gameplay mechanics - which are rather different to the D&D you're used to if you last played forty years ago. Tempting as it may be to dive in at the deep end, you might be better off setting aside everything you remember from the games you played before and starting at the very beginning with fresh eyes.

As the How To Play section of the Basic Rules describes making ability checks, attack rolls, and saving throws (the three main kinds of d20 roll, of which making a "Perception check" would be a wisdom-based ability check):

1. Roll the die and add a modifier.

Roll a d20 and add the relevant modifier. This is typically the modifier derived from one of the six ability scores, and it sometimes includes a proficiency bonus to reflect a character’s particular skill. (See "Step-By-Step Characters" for details on each ability and how to determine an ability’s modifier.)

2. Apply circumstantial bonuses and penalties.

A class feature, a spell, a particular circumstance, or some other effect might give a bonus or penalty to the check.

3. Compare the total to a target number.

If the total equals or exceeds the target number, the ability check, attack roll, or saving throw is a success. Otherwise, it’s a failure. The DM is usually the one who determines target numbers and tells players whether their ability checks, attack rolls, and saving throws succeed or fail.

The target number for an ability check or a saving throw is called a Difficulty Class (DC). The target number for an attack roll is called an Armor Class (AC).

This simple rule governs the resolution of most tasks in D&D play. "Using Ability Scores" provides more detailed rules for using the d20 in the game.