In terms of a round brilliant diamond, a properly cut stone should measure approximately 5.2 mm in diameter.
The size of a round .50 carat diamond in terms of the width is 5.06mm and the length 5.01mm.
One carat weight of diamond weighs .20 grammes, so your diamond is about half that weight, or roughly half a carat.
A forty-point diamond is nearly half a carat, which would be fifty points.
Generally, you would write .50 carat to represent a half-carat stone.
Half carat is the term used to measure the weight of the real diamond. A diamond's weight does not define or detract from the fact that the diamond is or is not a real diamond.
The total weight of all the diamonds combined in the carat total weight equals one half carat -- .50. The mm measurement of each individual diamond does not depend on the total carat weight of the collection.
A one-half carat diamond weighs 100 milligrams = 0.10 gram.
A 60-point diamond weighs just over half a carat (.50 carats). The size of the ring is not related to the weight of the diamond.
A half carat diamond of this cut measures 5.2 mm at the girdle; a .65 carat diamond measures 5.6 mm at the girdle. A certified gemologist can give you the exact carat weight of your 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."
A 1.00 point diamond is one carat, so a .12 point diamond is a little over 1/10th of a carat.
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.