See § Data values
For most items, there is a
(100 ÷ (level+1) )% chance that using the item reduces durability. On average, tools last
level+1 times as long.
(60 + (40 ÷ (level+1) ) )% chance a use reduces durability, meaning each durability hit against "unbreaking" armor has a 20%/27%/30% chance of being ignored. On average, armor lasts 25%/36%/43% longer.
|Enchantment||Namespaced ID||Numeric ID|