Diamonds are measued in carats, which is actually a term for how much a diamond weighs. Because diamonds can be cut with different proportions, such as depth and width, the weight is distributed differently per each diamond. For example, some diamonds can extremely deep, meaning that most of the weight is in the bottom of the stone. Regardless of the diamonds measurements, there is a general conversion chart that most diamonds fall under.
I'm assuming that you're referring to a round brilliant cut stone in this question, so Ill base the rest of my answer working under this assumption. In terms of the conversion chart, a 1 ct diamond is about 6.5mm wide.
I know that this information can be a bit confusing, and especially hard to understand in a short description such as this. There's a nice tutorial on diamond cut that discusses all of the information above in a detailed manner so you can better understand it. I added it to the "related links" that should show up under this posting.
A round 1 carat, D color, IF clarity diamond with excellent symmetry has a width of 6.4MM and a length of 6.36MM.
A 1.00 point diamond is one carat, so a .12 point diamond is a little over 1/10th of a carat.
A common misconception. Carat is nothing to do with size. Carat is related to weight and therefore a 1 carat stone depends on the gemstone in question and its cut. 1 carat is 0.2g and a 1 carat round-cut diamond is approximately 6.5mm in diameter. Similarly, since CZ is a diamond simulant, a 1 carat round-cut CZ is also deemed to be one that is 6.5mm in diameter but such a stone actually weighs more than 0.2g because CZ is more dense than diamond.
A carat is a measurement of diamond weight. From Amazon.com: "Carat is the unit of measurement used to describe the weight of diamonds. One carat is equal to 0.2 grams, or 0.007 ounces (avoirdupois). Five carats equals 1 gram, and 141.7 carats equals 1 ounce."
That depends on the cut, carat, color and clarity. For e.g, a round 1 carat D color, IF clarity, and an excellent cut diamond costs about $11, 081 and a 1 carat marquise diamond with the same characteristics costs about $17, 066, both of which are GIA certified.
One carat weight of diamond weighs .20 grammes, so your diamond is about half that weight, or roughly half a carat.
A one carat diamond weighs one carat, or .20 grammes.
A diamond is valued by its cut, clarity, carat weight and colour. A local jeweler can show you stones in this category.
A one carat diamond in the round brilliant shape measures aproximately 6.5mm at the girdle. If the diamond is another cut, measurements will be different.
You've given the carat weight of a diamond. 'Big', then, is based on the cut of the stone.
Carat is a weight, so its weight is one tenth of a carat or one tenth of .20 grams.
One carat diamond weight is equal to .20 grammes.
The price of a 1-carat diamond can vary widely depending on several factors, including the diamond's cut, color, clarity, and carat weight.