As carat weight gets larger the value of the diamond increases disproportionately. This is because pieces of rough material are increasingly rare with size. Over a million pieces of rough must be mined to find one piece large enough to produce a 1 carat finished diamond. This means that a diamond twice as large as an identical, smaller one may be three or more times as expensive, depending on the market.
Prices per carat change at certain size thresholds. For example, the price per carat will be less for a .90 F VS2 diamond than the price per carat for a 1.00 F VS2, which will be less than the price per carat for a 1.50 F VS2 diamond, even though the color and clarity are the same. If the diamond of your dreams is above your intended budget, you may want to think about purchasing a diamond of the same color and clarity just under the threshold of the weight that you have in mind. Of course, diamond manufacturers are aware of these price-making weights too, so most diamonds are produced to finish at or just above such thresholds.
