How many Banelings do I need to wipe different structures?

Solution 1:

Banelings deal 80 damage to buildings.

Supply Depots have 400 health == 5 Banelings

Command Centers have 1500 health == 19 Banelings

Pylons have 200 health and 200 shields == 5 Banelings

Nexus have 1000 health and 1000 shields == 25 Banelings

Destructible Rocks have 2000 health == 25 Banelings

All numbers are approximate, as they do not take armor into account (which may mean you require 1 more baneling to make up for mitigated damage)