Carat denotes the weight of a diamond, not the size. Two diamonds that have the same carat weight may actually have very different sizes in millimeters.
Typical range for Carat is between 1.0 and 2.0 carat.
A Diamond’s Weight is measured in Carats. One carat is equal to 200 milligrams, or 0.2 grams. The weight of smaller diamonds is often expressed as points instead of carats -- there are 100 points in a Carat. Another way to look at it is to say that each point equals 0.01, or One-Hundred, of a Carat. For example, 0.08 means eight One-Hundred, so a 0.08 Carat Diamond equals eight points.
NOTE: DON'T CONFUSE "CARAT WEIGHT" WITH "KARAT," WHICH IS THE METHOD OF DETERMINING THE PURITY OF GOLD.
A lot of people think that it is better to go for a bigger diamond while saving money on cut, color, or clarity.
You should keep in mind that even though larger stones are more visible, their imperfections are also more visible, such as natural flaws, yellowish tints or a nonsymmetrical cut.
If you want to go for a larger diamond, make sure the clarity is higher than VS2 and cut is excellent or very good.
Keep in mind that every diamond is different, so you will need to examine each stone carefully to make sure it is right for you.