Diamond size can vary depending on carat weight and overall cut proportion. A 1.00 carat stone that is cut a little too deep might actually be smaller looking than a 0.90 carat stone that is well proportioned. Also, at certain carat levels, per carat prices increase substantially. These carat levels are the following: 0.50ct, 0.70ct, 1.00ct, 1.50ct, 2.00ct, 3.00ct, 4.00ct., and 5.00ct.