Bounds for applied materials.

Let’s say I have a cube with two material elements applied on different faces. Now how do I find out the scale of the cube’s face (let’s say UV) where one element is applied.

From the image above, I have two materials on the face of the cube. How do I find the the scale(maybe in terms of bounds) of the cube with material element 0.
Is there any way to do this? I want the face of the object as well as the scale of the object covered by individual material on it.