The Diamond Carat Size Chart

When it comes to diamonds, carat is probably one of the attributes most often misunderstood as many believe carat refers to the actual size of a stone. In fact, carat refers to the weight of a diamond as opposed to its physical size, though the two are related. Beyond carat, a variety of factors can influence the apparent visual size of a diamond, including the diamond cut grade and shape of the stone. Together, these elements determine the price at which a diamond is sold to the consumer, whether natural diamonds or lab grown diamond alternatives. Understanding the influence of these factors will help you determine the best option for your budget for simulated diamond jewelry.


For carat size comparisons, it is easiest to see the differences when using a diamond size chart. One way to better understand it is to look at different shapes, like a round cut diamond, and how they will visually appear at different carat sizes. Here is a helpful carat size chart to aid you in visualizing how a diamond’s shape and carat influence how its physical size appears.


Carat Size: 0.25 ct 0.50 ct 0.75 ct 1.0 ct 1.5 ct 2.0 ct 3.0 ct 4.0 ct 5.0 ct
Round 4.1 mm 5.1 mm 5.8 mm 6.4 mm 7.4 mm 8.1 mm 9.3 mm 10.2 mm 11 mm
Cushion 4x3.5 mm 5x4.5 mm 6x5 mm 6.5x55 mm 7.5x6.5 mm 8x7 mm 9x8 mm 10x8.5 mm 10.5x9 mm
Princess 3.5 mm 4.4 mm 5 mm 5.5 mm 6.4 mm 7 mm 8 mm 9 mm 9.5 mm
Oval 5x3 mm 6x4 mm 7.5x5.5 mm 8x5.5 mm 9x6 mm 10.5x7 mm 11.5x7.5 mm 13x8.5 mm 14x9.5 mm
Emerald 4.5x3 mm 5.5x4 mm 6x4.5 mm 6.5x5 mm 7.5x5.5 mm 8.5x6 mm 9.5x7 mm 10.5x7.5 mm 11.5x8.5 mm
Radiant 3.5x3 mm 5x4.5 mm 5.5x5 mm 6x5.5 mm 7x6 mm 7.5x7 mm 8.5x7.5 mm 9.5x8.5 mm 10x9 mm
Pear 5.5x3.5 mm 7x4.5 mm 8x5 mm 8.5x5.5 mm 10x6.5 mm 10.5x7 mm 12.5x8 mm 13.5x9 mm 15x10 mm
Asscher 3.7 mm 4.4 mm 5 mm 5.5 mm 6.4 mm 7 mm 8.1 mm 9 mm 9.6 mm
Marquise 6.5x3.3 mm 8.5x4 mm 9.5x4.5 mm 10.5x5 mm 12x6 mm 13x6.5 mm 14x7 mm 16x8 mm 17x8.5 mm
Trillion 4.9 mm 6.1 mm 7 mm 7.7 mm 8.9 mm 9.8 mm 11.2 mm 12.3 mm 13.2 mm

While carat is the standard unit of measurement, the millimeter size measurement of a diamond tells you its true physical size. This is important when considering the faceting and shape because, as you can see in the diamond weight chart above, certain shapes will appear larger in size at equivalent carat weights. Oblong shapes specifically, such as emerald, oval, or pear, often look larger than their round counterparts. When shopping for diamonds, the carat weight, as well as millimeter measurements, can always be found on the Gemological Institute of America (GIA) certificate of the diamond.