Kari, this is a great chart, you should always ask for the millimeter size on different stones, because that is what you actually see. A one carat diamond is about 6.5mm and a one carat sapphire about 6mm because sapphires are heavier. Personally I would rather know how big it looks than what it weighs. A stone can be belly cut and deep and all that carat weight goes to waste under the mounting, unless of course you need it for saturation of color in certain types of stones.