Carat Weight

Carat Weight Explained

A carat is the unit of measurement used to weigh diamonds and other gemstones. One carat is equal to 200 milligrams, or 0.2 grams and is usually written as ct.

The word carat is derived from the seed from the fruit of the carob tree. The seeds are relatively uniform in weight and were once used throughout the Mediterranean basin as counterweights in simple balances. The word carat is supposedly derived from keration, the Greek name for the tree.

When you think about carat weight you should also think about millimeter size and diameters. The following diagram shows the relative size of various carat weights in a round brilliant cut diamond that is cut to the same proportions.

Ideally, round brilliant cut diamonds have the following minimum diameters:

0.50ct 0.70ct 1.00ct
5.1mm 5.7mm 6.3mm
1.20ct 1.50ct 2.00ct
6.9mm 7.3mm 8.00mm
3.00ct 4.00ct 5.00ct
9.3mm 10.1mm 10.8mm


Note: Use this chart as a relative guide only, actual sizes will vary with different monitor settings.