Carat Weight

Carat is the unit of measurement used to weigh diamonds and other gemstones.

Diamond Carat Weight

Image credit: GIA (image not to scale)

The last of the 4Cs is carat (weight). How much does a 1 carat diamond weigh? One carat (ct) is equal to 200 milligrams, i.e., 0.2 grams.

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

When thinking about carat weight, you should also consider the diamond's millimetre size and diameters. The diagram below shows the relative size of various diamond carat weights for a round brilliant cut diamond that is cut to the same proportions. endeavours to purchase round brilliant cut diamonds with the following minimum diameters:

0.5ct Diamond 0.7ct Diamond 1ct Diamond
0.50ct 0.70ct 1.00ct
5.1mm 5.7mm 6.3mm
1.2ct Diamond 1.5ct Diamond 2ct Diamond
1.20ct 1.50ct 2.00ct
6.9mm 7.3mm 8.00mm
3ct Diamond 4ct Diamond 5ct Diamond
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.

Next: Learn about Diamond Grading Reports