Capacity is a value possessed by both characters and Skills in the Tellius Series games, which determines how many Skills a character can equip at the same time. Characters can only equip Skills if their remaining Capacity is greater than or equal to the Capacity of the new Skill they're trying to equip. Once a Skill is equipped, the character's remaining Capacity is reduced by the Skill's new Capacity. In Fire Emblem: Radiant Dawn, natural Skills consume up zero Capacity (although once they are removed, this effect is lost forever). Characters can increase their Capacity by promoting. Laguz characters in Radiant Dawn can increase their Capacity by reaching level 15 or level 30.
In Fire Emblem: Path of Radiance, non-promoted foot units (and Mist) have 20 Capacity and gain 5 upon promotion. Mounted units start with 15 Capacity and gain 5 upon promotion. In Fire Emblem: Radiant Dawn 1st Tier classes have 15 Capacity (excluding Light Mage, which has 20), 2nd Tier classes have 30 and 3rd Tier classes have 60 (excluding Black Knight, which has 70). Laguz characters who are Level 14 or below have 20 Capacity, increasing to 35 when they are Level 15-29 and finally 70 when they are above Level 30. Certain Laguz characters, most notable the royals receive a bonus 30 Capacity, allowing them to reach a maximum of 100.
Skills cost 5 to 20 Capacity in Fire Emblem: Path of Radiance. The Herons' Galdrar Skill and Mastery Skills cost the most. In Radiant Dawn, Skills cost 5 to 30 Capacity. Stillness and three Mastery Skills cost 25 Capacity, while Glare and the other Mastery Skills cost 30.