Scaling and Rescaling of Objects.

I have a scene and objects in the scene were scaled and rescaled and then again rescailed to the point I complitely lost what the original scale was. Now I want to use physics and the right scale is critical. Is there a way to measure units in Unity? Is the cube object ALWAYS 1m*1m*1m(1 unit in unity = 1 meter) and I can just create a cube and rescale the objects to their proper scale using a cube as a one-meter unit?