Pathfinder has a variety of Skills, from Athletics to Medicine to Occultism. Each grants you a set of related Actions that rely on you rolling a skill check. Each skill has a Key Attribute modifier, based on the scope of the skill in question. For instance, Athletics deals with feats of physical prowess, like swimming and jumping, so its Key Attribute modifier is Strength. Medicine deals with the ability to diagnose and Treat Wounds and ailments, so its Key Attribute modifier is Wisdom. The Key Attribute modifier for each skill is listed in Chapter 4: Skills. No Matter which skill you’re using, you calculate a check for it using the following formula.
Skill check result = d20 roll + the skill’s Key Attribute modifier + Proficiency bonus + other Bonuses + Penalties
You’re unlikely to be trained in every skill. As normal, when using a skill in which you’re untrained, your Proficiency bonus is +0; otherwise, it equals your level plus 2 for trained, or higher once you become expert or better. The Proficiency rank is specific to the skill you’re using. Aid from another character or some other Beneficial situation may grant you a circumstance bonus. A Status bonus might come from a helpful spell or Magical effect. Sometimes tools related to the skill grant you an item bonus to your skill Checks. Conversely, unfavorable situations might give you a circumstance penalty to your skill check, while harmful Spells, magic, or conditions might also impose a Status penalty. Using shoddy or makeshift tools might cause you to take an item penalty. Sometimes a skill action can be an Attack, and in these cases, the skill check might take a multiple Attack penalty.
When an ability calls for you to use the DC for a specific skill, you can calculate it by adding 10 + your total modifier for that skill.
When the chance something will happen or fail to happen is based purely on chance, you’ll attempt a flat check. A flat check never includes any modifiers, Bonuses, or penalties—you just roll a d20 and compare the result on the die to the DC. Only abilities that specifically apply to flat Checks can change the checks’ DCs; most such Effects affect only certain types of flat Checks.
If more than one flat check would ever cause or prevent the same thing, just roll once and use the highest DC. In the rare circumstance that a flat check has a DC of 1 or lower, skip rolling; you automatically succeed. Conversely, if one ever has a DC of 21 or higher, you automatically fail.
Sometimes you as the player shouldn’t know the exact result and effect of a check. In these situations, the rules (or the GM) will call for a Secret check. The Secret trait appears on anything that uses Secret Checks. This type of check uses the same Formulas you normally would use for that check, but is rolled by the GM, who doesn’t reveal the result. Instead, the GM simply describes the information or Effects determined by the check’s result. If you don’t know a Secret check is happening (for instance, if the GM rolls a Secret Fortitude save against a Poison that you failed to notice), you can’t use any Fortune or Misfortune abilities on that check, but if a Fortune or Misfortune effect would apply automatically, the GM applies it to the Secret check. If you know that the GM is attempting a Secret check—as often happens with Recall Knowledge or Seek—you can usually activate Fortune or Misfortune abilities for that check. Just tell the GM, and they’ll apply the ability to the check.
The GM can choose to make any check Secret, even if it’s not usually rolled secretly. Conversely, the GM can let you roll any check yourself, even if that check would usually be Secret. Some groups find it simpler to have players roll all Secret Checks and just try to avoid acting on any out-of-character Knowledge, while others enjoy the mystery.
