Damage is a measure of how vulnerable one is to the knockback of attacks. A player's damage starts at 0% and can take any decimal number between 0% and 999%; however, the game only displays integers, so a damage displayed as 15% could be any number above 15% and below 16%. At low damages, the player cannot be knocked back very far, and can only be thrown off-stage by the game's most powerful attacks. At high damages, the player is knocked back considerably by most attacks, and is at increasing risk of being KO'd. Though damage is measured in percent, getting to 100% does not mean a character is doomed - the number itself is somewhat arbitrary.
Each attack deals a set amount of damage, which is then modified by things such as Stale Move Negation before the target is launched. An attack that does no damage will not cause targets to flinch and not produce a regular hit sound, although it will still cause knockback. The damage an attack deals is a significant factor in how much knockback it causes.
The following things are affected by damage:
- Knockback - As a character gets more damage, they fly further when hit. Certain attacks have set knockback, and don't apply.
- Grab time - Characters at high damage can be grabbed for longer.
- Status time - Generally, characters with higher damage are vulnerable for longer from a status effect (such as sleeping). The exception is being stunned though a shield breaking - the more damage a stunned character has, the faster they can recover.
- Ledge recovery - At 100%, a character's ledge animations become slower and provide more invincibility frames. The slower attack also deals more damage.
- Hoop damage - Characters stop getting hoop damage when at 150%.
- Jet Hammer - Like hoop damage, King Dedede stops getting damaged when at 150%.
- Lucario's attack power - The more damage Lucario has, the more damage his aura-based attacks do. The power caps at 182%, shown in SSBB's 25th single-player event match.
- Pikmin latch time - Pikmin release a character faster at higher damages.
- A Team Healer's healing power - The more damage the target has, the more damage the item heals.
- Swiming time - Higher-damaged characters have less time to swim before panicing, the shortest swim time being at about 90%.