The carat is the standard used to measure diamond weight.
The term carat refers back to ancient times when carob seeds were used as counterweights in merchants' hand-held balance scales.
These seeds were used because they are fairly uniform in size and weight. Until the twentieth century, "one caret" could range anywhere from 0.95 to 1.07 metric carats.
Now, with the international unit of measurement for gemstones, one carat equals 1/5 of a gram, and each carat is divided into 100 points. A one carat diamond is 100 points, therefore a 1/2 carat diamond is .50 ct, or "50 points".
Large diamonds are more rare than smaller ones, and as the carat weight increases, the value of the diamond rises. However, the increase is not directly proportionate to the size. For example, a one-carat diamond will cost more than twice that of a 1/2-carat diamond (assuming color, clarity, and cut are identical).
The Sales Associates at Ben Bridge Jeweler are trained and qualified to answer your questions and explain the differences between individual diamonds.
Weight does not always enhance the value of the diamond, either. Two diamonds of equal weight may be unequal in value, depending on other factors such as cut, color, and clarity.