The price of a 1.25 carat diamond, like any other diamond, is determined through a mixture of different factors known as the four Cs: carat weight, reduce, colour, and readability. those elements, along side market call for and other subjective elements, make contributions to the general fee and pricing of a diamond.Carat weight refers to the size of the diamond, with one carat equal to 0.2 grams. normally, as the carat weight will increase, the rate in step with carat has a tendency to increase as properly because large diamonds are rarer.