Ratios are a calculation of proportion when measuring the Length & Width of a stone. One of the key advantages of having this choice is to allow you to have the shape which is more appealing or flattering to you.
To calculate the ratio you divide the length by the width, leaving you with 1.(??) figure.
Whilst ratio is a personal preference, the most desirable ratios (found in Diamonds) are between 1.3 - 1.5
Below are the ratios of our common Oval cuts.
These sizes are what we offer for our Astral Moissanite™ pieces 
7 x 5mm 1.4
8 x 5mm 1.6
8 x 8.5mm 1.45
8 x 6mm 1.33
9 x 6mm 1.5
9x7mm 1.28
what we offer for our Asczdxvdv