The mm size of a diamond stone relative to its weight in carats is directly related to the cut and the excellence of the cut.
For example, a round brilliant stone measuring 8 mm in diameter at the girdle weighs about two carats. A different cut will have a different weight in carats.
Approximately between a 2 carat and a 2.50 carat.
This diamond may weigh between 1.75 (7.8MM) and 2.00 carats (8.2MM). The millimeter measurement is the diameter of the girdle, and depending on the cut, this diamond may weigh more or less than indicated, above.
There are 45.52 carats on the hope diamond
An 8mm x 8mm cushion cut is about 2.5 carats. But a jeweler or gemologist is better able to weigh the stone physically so that you have an accurate weight.
45.52 CaratsThe Hope Diamond is 45.52 carats. By comparison the average engagement ring is only 0.3 carats.
A round cut diamond weighing .25 carats measures 4.1mm at the girdle.
According to Wikipedia, below, this diamond weighs "755.5 carats (151 g)."
A round cut diamond weighing .25 carats measures 4.1mm at the girdle.
This diamond could weigh about six carats if its measurement is 10mm x 10mm.
If the diamond is measured in points -- 106, you could translate this to 1.06 carats.
From Wikipedia: "The Cullinan diamond is the largest rough gem-quality diamond ever found, at 3,106.75 carats (621.35 g)."
You can read more about the Spirit of de Grisogono black diamond, below, which weighs 312.24 carats.
The answer depends on the weight of each diamond. If each diamond weighs one carat, then in total you have 275 carats.