Diamond Carat Weight
A carat is a unit of measurement, it is the unit used to weigh a diamond and most other gemstones. One carat is equal to 200 milligrams, or 0.2 grams.
The word "carat" is taken from the carob seeds that people once used in ancient times to balance scales. So uniform in shape and weight are these little seeds that even today's sophisticated instruments cannot detect more than three one-thousandths of a difference between them.
Don't confuse "carat weight" with "karat," the method of determining the purity of gold.
Diamonds of large size are more rare than diamonds of smaller size; therefore, the price of larger diamonds is exponentially larger than the price of smaller diamonds. A one carat diamond solitaire ring is nearly always more expensive than a diamond ring made up of multiple diamonds that are similar, but smaller, even though they total one carat or more.
Carat Weight vs. Size
Carat weight is used as a measure for many gemstones, but different gems of the same weight aren't necessarily the same size, because some gemstones are more dense than others, meaning that they pack more weight into a smaller space.
Since diamonds are measured by carat weight, and not size, two diamonds of the same weight could have different sizes. If a diamond is cut too shallow it will have a larger diameter but a smaller depth. Likewise, if a diamond is cut too deep (or bottom heavy) it will have a smaller diameter and thus appear smaller when viewed from the top.
Weight of Small Diamonds
The weight of smaller diamonds is often expressed as points, not carats. There are 100 points in a carat. Another way to look at it is to say that each point equals 0.01, or one-hundredth, of a carat.
Point Examples
- 0.05 means five one-hundredths, so a 0.05 carat diamond equals five points.
- 0.25 means twenty-five one-hundredths, so a 0.25 carat diamond equals twenty-five points--or one quarter of a carat.
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Round
Diamond Size vs. Carat Weight |
| Milimeters |
Carat weight |
Points |
| 1.0 |
0.005 |
0.5 |
| 1.3 |
0.01 |
1 |
| 1.5 |
0.015 |
1.5 |
| 1.7 |
0.02 |
1 |
| 1.8 |
0.025 |
2.5 |
| 2.0 |
0.03 |
3 |
| 2.1 |
0.035 |
3.5 |
| 2.2 |
0.04 |
4 |
| 2.4 |
0.05 |
5 |
| 2.5 |
0.06 |
6 |
| 2.7 |
0.07 |
7 |
| 2.8 |
0.08 |
8 |
| 2.9 |
0.09 |
9 |
| 3.0 |
0.10 |
10 |
| 3.1 |
0.11 |
11 |
| 3.2 |
0.12 |
12 |
| 3.3 |
0.14 |
14 |
| 3.4 |
0.15 |
15 |
| 3.5 |
0.16 |
16 |
| 3.6 |
0.17 |
17 |
| 3.7 |
0.18 |
18 |
| 3.8 |
0.20 |
20 |
| 3.9 |
0.22 |
22 |
| 4.0 |
0.25 |
25 |
| 4.2 |
0.30 |
30 |
| 4.4 |
0.33 |
33 |
| 4.5 |
0.35 |
35 |
| 4.6 |
0.38 |
38 |
| 4.8 |
0.40 |
40 |
| 5.0 |
0.50 |
50 |
| 5.4 |
0.60 |
60 |
| 5.5 |
0.63 |
63 |
| 5.6 |
0.65 |
65 |
| 6.0 |
0.75 |
75 |
| 6.4 |
0.95 |
95 |
| 6.6 |
1.00 |
100 |
| 6.8 |
1.17 |
117 |
| 7.0 |
1.25 |
125 |
| 7.2 |
1.33 |
133 |
| 7.5 |
1.55 |
155 |
| 7.8 |
1.75 |
175 |
| 8.0 |
2.00 |
200 |
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