Skills

Getting Skills
At each level, a character gets skill points that are used to buy skills. The character's class and Intelligence modifier determine the number of points received.

If the character buys a class skill, he or she gets 1 rank in the skill for each skill point spent. If the character buys a cross-class skill, he or she gets 1/2 rank per skill point. The maximum rank in a class skill is equal to character level + 3. The maximum rank in a cross-class skill is one-half of this number.

Using Skills
To make a skill check, roll:

1d20 + skill modifier

(Skill modifier = skill ranks + ability modifier + miscellaneous modifiers)

Skill Ranks: A character's ranks in a skill is based on the number of skill points the character has invested in the skill. Some skills can be used even if the character has no ranks in the skill; doing this is known as making an untrained skill check.

Ability Modifier: The ability modifier used in the skill check is the modifier for the skill's key ability (the ability associated with the skill's use). The key ability of a skill is noted in its description.

Miscellaneous Modifiers: Miscellaneous modifiers include bonuses provided by feats and class features, and penalties such as the ones associated with the nonproficient use of armor, among others.

Acquiring Skill Ranks
Ranks indicate how much training or experience a character has with a given skill. Each skill has a number of ranks, from 0 (for a skill in which a character has no training at all) to 23 (for a 20th-level character who has increased a class skill to its maximum rank). When making a skill check, a character adds his or her skill ranks to the roll as part of the skill modifier.

The rules assume that a character can always find a way to learn any skill. However, the GM can impose limits depending on circumstances and a given situation.

Skill Checks
Unlike with attack rolls and saving throws, a natural roll of 20 on the d20 is not an automatic success when making a skill check, and a natural roll of 1 is not an automatic failure.

Difficulty Class
Some checks are made against a Difficulty Class (DC). The DC is a number set by the GM (using the skill rules as a guideline) that a character must attain to succeed.

Opposed Checks
Some skill checks are opposed checks. They are made against a randomized number, usually another character's skill check result.

For ties on opposed checks, the character with the higher key ability score wins. If those scores are the same, roll again.

Untrained Skill Checks
Generally, if a character attempts to use a skill he or she doesn't have any ranks in, the character makes a skill check as described. The character's skill modifier don't include skill ranks because the character doesn't have any. The character does get other modifiers, though, such as the ability modifier for the skill's key ability.

Some skills can be used only if the character is trained in the skill.

Tools
Some skill applications require the use of tools. If tools are needed, the specific items required are mentioned in the skill description. If the character doesn't have the appropriate tools, he or she can still attempt to use the skill, but the character takes a -4 penalty on his or her check.

A character may be able to put together some impromptu tools to make the check. If the GM allows it, reduce the penalty to -2 (instead of -4) for using impromptu tools. It usually takes some time (several minutes to an hour or more) to collect or create a set of impromptu tools, and it may require a skill check as well.

Ability Checks
Sometimes a character tries to do something to which no specific skill applies. In these cases, the character makes an ability check: Roll 1d20 and apply the appropriate ability modifier. The GM assigns a DC, or sets up an opposed check when two characters are engaged in a contest using one ability against another. In some cases, a test of one's ability doesn't involve luck. When two characters arm wrestle, for example, the stronger character simply wins. In the case of identical scores, make opposed Strength checks.