Minecraft wiki entry for Drops, associated text: Rare drops typically have a 2.5% chance of dropping, plus 1 percentage point per level of Looting on the weapon used (up to a maximum of 5.5% with Looting III). An exception to this is that a rabbit drops a rabbit's foot with a 10% chance, plus 3 percentage points per level of Looting (to a maximum of 19% with Looting III). in Bedrock Edition there are other exceptions: a Wither Skeleton drops a Wither skull with a 2.5% chance plus 2 percentage points per level of looting (to a maximum of 8.5% with Looting III), and a drowned drops a copper ingot with an 11% chance plus 2 percentage points per level of looting (to a maximum of 17% with Looting III).