Examples herein describe systems and methods for hanger placement for computer-aided design (“CAD”). A plugin can provide a hanger placement option on a graphical user interface (“GUI”) of the CAD program. When the option is selected, the plugin can choose hanger locations on a run of ductwork or piping based on hanger parameters and collision detection. This can include testing hanger locations by building an array between the selected item and the ceiling of a plan in the GUI, and testing for collisions with other objects at each point in the array. If a collision is detected, a new hanger location is tested. The new hanger location can be selected based on the hanger parameters, such as by incrementing the interval between hangers while staying within a maximum interval.