How do I determine unity "unit" size of a model?

I have purchased some models. When the models are loaded into unity, their scale is reported as 1x1x1, but they take up 2x4x6 units (when I move them around with position). Is there a way to determine how many units a model takes up at runtime, or must I create a big table that says “prefab 1” is 2x4x6, “prefab 2” is 2x2x4, and so on?

“Scale” is a scale factor: 1x1x1 simply means that the object is being rendered in its original scale, not that it occupies only 1x1x1 units.

To determine the volume that a model occupies, you can use mesh.bounds.