When your character uses a skill, he isn't guaranteed success. In order to determine success, whenever you attempt to use a skill, you must make a skill check.
Each skill rank grants a +1 bonus on checks made using that skill. When you make a skill check, you roll 1d20 and then add your ranks and the appropriate ability score modifier to the result of this check. If the skill you're using is a class skill (and you have invested ranks into that skill), you gain a +3 bonus on the check. If you are not trained in the skill (and if the skill may be used untrained), you may still attempt the skill, but you use only the bonus (or penalty) provided by the associated ability score modifier to modify the check. Skills can be further modified by a wide variety of sources—by your race, by a class ability, by equipment, by spell effects or magic items, and so on. See Table: Skill Check Bonuses for a summary of skill check bonuses.
|Skill||Skill Check is Equal To*|
|Untrained||1d20 + ability modifier + racial modifier|
|Trained||1d20 + skill ranks + ability modifier + racial modifier|
|Trained Class Skill||1d20 + skill ranks + ability modifier + racial modifier + 3|
|* Armor check penalty applies to all Strength- and Dexterity-based skill checks.|
If the result of your skill check is equal to or greater than the difficulty class (or DC) of the task you are attempting to accomplish, you succeed. If it is less than the DC, you fail. Some tasks have varying levels of success and failure depending on how much your check is above or below the required DC. Some skill checks are opposed by the target's skill check. When making an opposed skill check, the attempt is successful if your check result exceeds the result of the target.
A skill check represents an attempt to accomplish some goal, usually while under some sort of time pressure or distraction. Sometimes, though, a character can use a skill under more favorable conditions, increasing the odds of success.
Taking 10: When your character is not in immediate danger or distracted, you may choose to take 10. Instead of rolling 1d20 for the skill check, calculate your result as if you had rolled a 10. For many routine tasks, taking 10 makes them automatically successful. Distractions or threats (such as combat) make it impossible for a character to take 10. In most cases, taking 10 is purely a safety measure—you know (or expect) that an average roll will succeed but fear that a poor roll might fail, so you elect to settle for the average roll (a 10). Taking 10 is especially useful in situations where a particularly high roll wouldn't help.
Taking 20: When you have plenty of time, you are faced with no threats or distractions, and the skill being attempted carries no penalties for failure, you can take 20. In other words, if you a d20 roll enough times, eventually you will get a 20. Instead of rolling 1d20 for the skill check, just calculate your result as if you had rolled a 20.
Taking 20 means you are trying until you get it right, and it assumes that you fail many times before succeeding. Taking 20 takes 20 times as long as making a single check would take (usually 2 minutes for a skill that takes 1 round or less to perform).
Since taking 20 assumes that your character will fail many times before succeeding, your character would automatically incur any penalties for failure before he or she could complete the task (hence why it is generally not allowed with skills that carry such penalties). Common "take 20" skills include Disable Device (when used to open locks), Escape Artist, and Perception (when attempting to find traps).
Ability Checks and Caster Level Checks: The normal take 10 and take 20 rules apply for ability checks. Neither rule applies to concentration checks or caster level checks.
You can help someone achieve success on a skill check by making the same kind of skill check in a cooperative effort. If you roll a 10 or higher on your check, the character you're helping gets a +2 bonus on his or her check. (You can't take 10 on a skill check to aid another.) In many cases, a character's help won't be beneficial, or only a limited number of characters can help at once.
In cases where the skill restricts who can achieve certain results, such as trying to open a lock using Disable Device, you can't aid another to grant a bonus to a task that your character couldn't achieve alone. The GM might impose further restrictions to aiding another on a case-by-case basis as well.
|Difficulty (DC)||Example (Skill Used)|
|Very easy (0)||Notice something large in plain sight (Perception)|
|Easy (5)||Climb a knotted rope (Climb)|
|Average (10)||Hear an approaching guard (Perception)|
|Tough (15)||Rig a wagon wheel to fall off (Disable Device)|
|Challenging (20)||Swim in stormy water (Swim)|
|Formidable (25)||Open an average lock (Disable Device)|
|Heroic (30)||Leap across a 30-foot chasm (Acrobatics)|
|Nearly impossible (40)||Track a squad of orcs across hard ground
after 24 hours of rainfall (Survival)
Some checks are made against a Difficulty Class (DC). The DC is a number (set using the skill rules as a guideline) that you must score as a result on your skill check in order to succeed.
An opposed check is a check whose success or failure is determined by comparing the check result to another character's check result. In an opposed check, the higher result succeeds, while the lower result fails. In case of a tie, the higher skill modifier wins. If these scores are the same, roll again to break the tie.
|Task||Skill (Key Ability)||Opposing Skill (Key Ability)|
|Con someone||Bluff (Cha)||Sense Motive (Wis)|
|Pretend to be someone else||Disguise (Cha)||Perception (Wis)|
|Create a false map||Linguistics (Int)||Linguistics (Int)|
|Hide from someone||Stealth (Dex)||Perception (Wis)|
|Make a bully back down||Intimidate (Cha)||Special1|
|Sneak up on someone||Stealth (Dex)||Perception (Wis)|
|Steal a coin pouch||Sleight of Hand (Dex)||Perception (Wis)|
|Tie a prisoner securely||CMB +20||Escape Artist (Dex)|
In general, you can try a skill check again if you fail, and you can keep trying indefinitely. Some skills, however, have consequences of failure that must be taken into account. A few skills are virtually useless once a check has failed on an attempt to accomplish a particular task. For most skills, when a character has succeeded once at a given task, additional successes are meaningless.
Generally, if your character attempts to use a skill he or she does not possess, you make a skill check as normal. The skill modifier doesn't have a skill rank added in because the character has no ranks in the skill. Any other applicable modifiers, such as the modifier for the skill's key ability, are applied to the check.
Many skills can be used only by someone who is trained in them.
Some situations may make a skill easier or harder to use, resulting in a bonus or penalty to the skill modifier for a skill check or a change to the DC of the skill check.
The chance of success can be altered in four ways to take into account exceptional circumstances.
Conditions that affect your character's ability to perform the skill change the skill modifier. Conditions that modify how well the character has to perform the skill to succeed change the DC. A bonus to the skill modifier and a reduction in the check's DC have the same result: They create a better chance of success. But they represent different circumstances, and sometimes that difference is important.
Using a skill might take a round, take no time, or take several rounds or even longer. Most skill uses are standard actions, move actions, or full-round actions. Types of actions define how long activities take to perform within the framework of a combat round (6 seconds) and how movement is treated with respect to the activity. Some skill checks are instant and represent reactions to an event, or are included as part of an action.
These skill checks are not actions. Other skill checks represent part of movement.
The normal take 10 and take 20 rules apply for ability checks. Neither rule applies to caster level checks.
Sometimes a character tries to do something to which no specific skill really applies. In these cases, you make an ability check. An ability check is a roll of 1d20 plus the appropriate ability modifier. Essentially, you're making an untrained skill check.
In some cases, an action is a straight test of one's ability with no luck involved. Just as you wouldn't make a height check to see who is taller, you don't make a Strength check to see who is stronger.