Add object of certain size I am trying to add a cubed object of certain dimensions instead of the default cube. I have looked over the documentation and can't see a way to do this.

To clarify. I'm looking for a 3D program that acts like CAD in that if I want to add an object in SI units I can. Eg 10mm x 25mm x 12.5mm. Or I want to change an object created by someone else. Scale does me no good if I don't have reference to the current size and units, and I'm not sure why anyone would want or need to do all that work when the rest of the world understands units.
Use the operator size after you add a mesh in Blender 2.79

Blender 2.79b



Use the operator size after you add a mesh in Blender 2.79 in the Add Cube panel

Blender 2.81