In order to calculate the diamond ratio, divide its length by width. For instance, a diamond that is 5.5 millimeters long and 3.5 millimeters wide has a 1.57 length to width ratio. When applied to an oval diamond ring, this ratio is at its most appealing if they are chosen in between 1.30 to 1.50. Vintage oval cut facets are appealing on the ring finger. However, a touch thinner diamond cut to that may look decorative in settings where diamonds are sided by stones. That is why personal style preference is up to the wearer when it comes to buying rings featuring an oval cut diamond. The oval shape engagement ring hides the birthmarks and impurities of the diamond. Next to the rounded edge, or where jewelry settings would lay, it is virtually implausible for onlookers to see inclusions of the diamond. This is one of the reasons, why diamond cutters suggest buying an oval diamond ring with SI1 or S12 clarity when on a tight budget.