Largest size calculator
 

What do I need to do to create a calculator that will tell me how large an item I can fit through a door?
Obviously I know height and width but what if there is an obstruction ie a back wall that will not allow the full length into the room. Or a ramp leading up to the door that would mean I may strike the roof.
I can angle the box in the doorway and turn it to get it in. What calculation should I use?
I would have the following input data: height,width,length and weight(after a certain weight it becomes impossible to move without rollers which would add height) of the box. The height and width of the door. The distance from the door of the walls.
Thanks
Nobby