A skill rank is a number indicating how much training or experience a character has with a given skill. Skill rank is incorporated into the skill modifier, which in turn improves the chance of success for skill checks with that skill.
A character's number of ranks in a skill is based on how many skill points a character has invested in it. It is possible to collect up to five skill points and stack them until needed; they do not have to be spent at level-up.
Many skills can be used even if the character has no ranks in them; doing so is called making an untrained skill check.
Acquiring skill ranks
For class skills (such as listen for a rogue or spellcraft for a cleric), a character gets 1 rank (equal to a +1 bonus on checks with that skill) for each skill point. For cross-class skills, a character gets a ½ rank per skill point invested.
Maximum skill ranks
The maximum skill ranks of a skill represents the highest achievement a character can reach at his current level.
- Class Skill: The maximum skill ranks for a character's class skill is equal to the that character's character level + 3.
- Cross-class Skill: The maximum skill ranks for a character's cross-class skill is equal to the (character level + 3) ÷ 2.
- Cross-class skills in NWN had a max skill rank equal to (character level + 3) ÷ 2, with the final figure rounded down (e.g. the max cross-class rank of a character with 4 character levels would be 3).