The formula for damage reduction by projectiles is
level × 8%, meaning for every additional level another 8% of the damage is absorbed. The highest level (Projectile Protection IV) absorbs 32% (
4 × 8%) of the damage inflicted by any projectiles. Theoretically at level 13 and above no damage by projectiles are possible (because it would transcend 100%), but absorbed damage is capped at 80%, which means that level 10 is the highest that will give any effect.
Protection, Blast Protection, Fire Protection, and Projectile Protection are mutually exclusive. However, if commands are used to have two or more of these enchantments on the same item, the effects stack.
|?||Added Projectile Protection|
|1.14||?||Protection enchantments are no longer mutually exclusive.|
|1.14.3||pre2||Protection enchantments are mutually exclusive again.|
|Pocket Edition Alpha|
|0.12.1||build 1||Added Projectile Protection|