Carat - The easiest of the five c's to understand. The "carat" is a measure of weight. The larger the diamond is the larger the carat weight figure will be. Many times you will hear the term "points" in reference to diamond weight. If you think of 1 carat as 1.00 dollar, then a ¾ carat diamond is .75 cents or 75 "points". It is expressed as .75 ct. When you see ".ctw" after a weight it means that more than one diamond adds up to a total combined weight of three quarters of a carat. CTW means "carat total weight".
It is important to understand that the value of diamonds increases exponentially. By that we mean that a one carat diamond (1.00 ct) can cost much more that simply twice the price of a half carat diamond (.50 ct) even though it weighs twice as much.Diamond Shape and Carat Reference:
What size (carat) diamond should I buy?