There are no measurements to describe how to find your perfect diamond. However important the 4 C`s are - beauty is the only arbiter. All diamonds should show Fire, Life, and Brilliance.
Fire is the beautiful rainbow effect that is produced by the dispersion of light, Life is the scintillation and sparkle when you move the stone in front of your eyes, and Brilliance is the brightness of the diamond due to reflected white light when the diamond is still.
Ultimately though, it is the diamond that chooses you. Lesser diamonds can be cut for weight but their lack of Fire, Life, and Brilliance is seen and remembered long after the cost is forgotten