An Intro to Gemstone Size

Gemstone size is measured in carat weight and surface dimensions. Carat weight indicates how heavy a gemstone is, but it’s not the best measure of a gemstone's visual size. That’s because different gemstones have different densities, which means that two gemstones with the same carat weight won't necessarily have the same proportions. For example, a two-carat ruby is smaller than a two-carat diamond, but it’s denser, so it weighs the same as a less-dense diamond.

In general, larger gemstones are more valuable than smaller gemstones. You’ll often pay less by buying more, smaller gems that add up to a certain weight than a single gemstone of the same weight. For example, four ½-carat emeralds or rubies will cost less than a single, two-carat emerald or ruby.

Gemstone dimensions paint a more accurate picture of a gemstone's size as viewed from above. You can visualize how much of a gemstone is showcased in its setting by noting its diameter, length or width.