The final of the 4Cs is Carat Weight – the literal weight of a diamond. Of course, this also determines the overall size of the diamond. However, bigger doesn’t always mean better in this case, as all 4Cs – Colour, Clarity, Cut, and Carat – need to be considered in the final evaluation, ranking and value of the diamond.
One metric carat is equal to 200 milligrams. The modern carat system evolved with the carob seed. Early gem traders used the small, uniform seeds as counterweights in their balance scales. A carat is the same gram weight in every corner of the world. Which means no matter where you may find yourself in the world, the heavier the diamond, the rarer and more desirable it becomes. Because of this, one single carat diamond is worth more than four 0.25-carat stones together.
To determine carat weight, the diamond is weighed using an extremely accurate electronic micro-balance that captures the weight to the precise fifth decimal place (the nearest ten-thousandth of a carat).
A Carat is not to be confused with a Karat (abbreviated to “K” or “Kt”), which is a unit of measure that describes the purity of gold – which is another important part in the ring purchasing process.