The below table shows the changing dynamic between an increase in carat size and the respective increase in a marquise cut diamond's visual appearance as measured by surface area. While carat weight is typically thought of as the best indication of a diamond's size (meaning visual appearance), carat is actually a measure of weight. Diamonds of the same carat size can vary slightly in their visual appearance depending on how they are cut. For instance, a diamond with a deeper cut will appear smaller than a diamond of the same carat weight with a shallower cut.
For our marquise cut diamond analysis we averaged the diameters of hundreds of thousands to come up with a simple exponential function (shown on the chart below). Using this formula we can study the corresponding changes in diameter and surface area for a given change in carat weight. Interestingly, as the carat size increases we notice a significant slowing of the surface area. This is because carat weight scales as a measure of volume (mm cube) while surface area scales at a slower rate (mm squared).
|Carat||Surface Area (sq. mm)|