Experts define carat as a measure of a diamond's weight. As carat by itself will not accurately show a diamond's size, we view it from the top. This is done because that is how we view diamonds when they are given to us set in a ring.
To understand diamond size, carat weight should be considered in conjunction with two other criteria, namely, distance in millimetres across the top of the diamond and the gem's cut grade.
Diamond Carat Size Chart
This print out illustrates how diamonds of different carat weights and shapes will appear when viewed from the top down.
Your diamond may differ from the printout in length/width ratio, table, and depth
While deciding on carat weight, it is important to measure the distance across the top of the diamond as this is how we view a stone when set into a ring
A diamond's cut grade must also be considered because when a diamond is cut with the proper proportions, the maximum amount of light is returned out of the top of the diamond. Thus, when a diamond is well cut, the light reflected out of the top makes it appear larger. In addition, much of the weight of a poorly cut diamond may be "hidden" in its base, thus making the diamond appear smaller than its actual carat weight.
It is therefore possible to have a diamond of a lower carat weight, but of higher cut grade that appears larger than a diamond with a larger carat weight, but with a poor cut.
This chart illustrates how diamonds of different carat weights look when set in a ring. Note that a 2-carat diamond does not appear to be twice the size of a 1-carat diamond when viewed from the top.
choosing diamond size
What Carat Weight Is Right For Me?
The important factors determining the carat weight of a diamond are the correct finger size, the size of your setting, and also your budget.
If a large carat weight is what you want and you have budget constraints, opt for a diamond with a good cut, SI1-SI2 clarity, and I or J color grade.
Diamond prices are the highest at the full and half-carat weights. Gems just below these weights cost a lot lesser, and as carat weight is distributed across the whole diamond, small size differences are almost impossible to detect.
Another factor to be considered is the size of the finger; the smaller the finger, the larger the diamond will appear. A 1.5-carat diamond solitaire looks much larger on a size 4 finger than on a size 8.