Diamond Carat Weight: Size Chart and Buying Tips | Blue Nile
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Diamond Carat Weight

Diamond carat is often misunderstood and refers to a diamond's weight, not necessarily its size. When comparing diamond carat sizes, take a diamond's cut into consideration as well: a high-carat diamond with a poor cut grade may look smaller, often cut deeper, than a diamond with smaller carat weight and a better cut. Use our buying tips, diamond carat size chart, and expert tips to help you choose the best diamond carat weight for you.

Buying Tips

  • Carat is the most misunderstood of the 4Cs. It actually refers to a diamond's weight, not the diamond’s size.
  • Consider cut and carat together; a larger carat diamond with a poor cut grade can appear smaller than a smaller diamond with a higher cut grade.
  • To maximise your budget, "Buy Shy," which means selecting a carat weight slightly below the whole and half carat marks. For example, instead of a 2.0-carat diamond, consider buying a 1.9-carat weight. This will save a considerable amount of money and the slight size difference will never be noticed.
1.5 Carat Diamond Example
0.25
0.5
0.75
1.0
1.5
2.0
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4.0
5.0

1.5 Carat Diamond

Keep in mind, diamond prices increase exponentially with carat weight because the larger the carat, the more rare the diamond.
See 1.5 Carat Diamonds

Diamond Carat Size Chart

This print out illustrates differences in diamond size based on carat weight, and 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.

Download Chart
Diamond Carat Size Chart

Carat Weight considers two factors:

  1. A Diamond's Top Diameter
    It is important to measure, in millimeters, the distance across the top (diameter) of the diamond as this is how it is viewed when set into a ring.
  2. A Diamond's Cut Grade
    A diamond's cut grade should also be considered. When a diamond is well cut (grades Very Good or higher), the light reflected out of the top making it appear larger.

How do these two Carat Weight factors help when purchasing a diamond?

The diamond's diameter and cut grade reveal that smaller carat weight diamonds will appear larger with higher cut grades (Very Good and Ideal). On the flip side, a larger carat weight diamond could appear smaller with lower cut grades (Good, Fair and Poor).

More Expert Tips

  • If a large carat weight is important to you, yet you're working within a strict budget, consider a diamond with a good cut, SI1-SI2 clarity, and an I or J colour grade.
  • Diamond prices jump at the full- and half-carat weights. Diamonds just below these weights cost significantly less, and, because carat weight is distributed across the entirety of the diamond, small size differences are almost impossible to detect.
  • Keep in mind that 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 a size 8.
  • Not all settings will fit all diamond carats or shapes. If you have already selected a setting, check the diamond specifications of your ring or ask your Blue Nile Diamond and Jewellery Consultant (800-852-3878) for help. If you need a special jewellery piece created, Blue Nile can accommodate almost any request.

Next, learn about Diamond Cut.

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