Sapphire rings are valued using the 4 "Cs", same as diamond rings and other precious gemstones. Below are the most important factors in valuing sapphire rings:
The weight of the sapphire(s) within the ring is measured in carats. Common carat weight examples inclue 1,2, and 3 carat sapphire rings.
The cut of a sapphire ring doesn't refer to the shape of the sapphire, but rather the quality of the cut and it's ability to interact with or refact light.
The clarity of a sapphire ring is measured in the same nomenclature as diamonds. Internally flawless sapphire rings are the highest clarity.
The color of your sapphire ring is directly correlated to the value. Deep blue sapphire rings represent the clearest hue of sapphire and command the highest prices.