Ruby rings are valued using the 4 "Cs", same as diamond rings and other precious gemstones.
Below are the most important factors in valuing ruby rings:
The weight of the ruby or rubies within the ring is measured in carats. The most common carat weights are between .5 carats and 2 carats.
The cut of a ruby ring doesn't refer to the shape of the ruby, but the quality of the cut and it's ability to interact with or refact light.
The clarity of a ruby ring is measured in the same manner as diamonds. Internally flawless ruby rings are the highest clarity.
Ruby rings may only be the color red. Deep red ruby rings typically fetch the highest prices.