Carat Weight
Diamond and most other gem weights are expressed in metric carats. One metric carat equals 0.200 grams (200 milligrams or 1/5 gram). A carat is divided into 100 equal units called "points or Cent." According to US Federal Trade Commission rulings, all weight representations are subject to a 1/200 carat (one-half "point") tolerance.
Diameter and Weight
| Diameter
|
Approx. Weight
|
|
4.10 mm
|
0.25 ct
|
|
5.20 mm
|
0.50 ct
|
|
6.50 mm
|
1.00 ct
|
|
7.40 mm
|
1.50 ct
|
|
8.20 mm
|
2.00 ct
|
Weight Ranges
| Fraction
|
Avg. Weight Range
|
| 9/10
|
.90 - .95 ct
|
| 7/8
|
.84 - .89 ct
|
| 3/4
|
.70 - .83 ct
|
| 5/8
|
.57 - .69 ct
|
| 1/2
|
.47 - 56 ct
|
| 3/8
|
.38 - .46 ct
|
| 1/3
|
.30 - .37 ct
|
| 1/4
|
.23 - .29 ct
|
| 1/5
|
.18 - .22 ct
|
| 1/6
|
.15 - .17 ct
|
| 1/8
|
.12 - .14 ct
|
| 1/10
|
.09 - .11 ct
|
Small Weights
| Spoken
|
Decimal
|
Recorded
|
| Eights
|
.125 ct
|
1/8
|
| Tens
|
.10 ct
|
1/10
|
| Thirty-Threes
|
.03 ct
|
1/33
|
| Fifties
|
.02 ct
|
1/50
|
| Seventies
|
.015 ct
|
1/70
|
| Hundreds
|
.01 ct
|
1/100
|
| One Twenty-Fives
|
.008 ct
|
1/125
|
| One Fifties
|
.007 ct
|
1/150
|
| Two Hundreds
|
.005 ct
|
1/200
|
Estimating Melee Weights By Diameter
| Full Cuts
|
| Diameter
|
Apporx. Weight
|
| 1.3 mm
|
0.01 ct
|
| 1.7 mm
|
0.02 ct
|
| 1.8 mm
|
-
|
| 1.9 mm
|
-
|
| 2.0 mm
|
0.03 ct
|
| 2.1 mm
|
-
|
| 2.2 mm
|
0.04 ct
|
| 2.3 mm
|
-
|
| 2.4 mm
|
0.05 ct
|
| 2.5 mm
|
-
|
| 2.6 mm
|
0.06 ct
|
| 2.7 mm
|
0.07 ct
|
| 2.8 mm
|
0.08 ct
|
| 2.9 mm
|
0.09 ct
|
| 3.0 mm
|
0.10 ct
|
| 3.1 mm
|
0.11 ct
|
| 3.2 mm
|
0.125 ct
|
| 3.3 mm
|
0.14 ct
|
| 3.4 mm
|
0.15 ct
|
| 3.5 mm
|
0.16 ct
|
| 3.6 mm
|
0.17 ct
|
| 3.7 mm
|
0.18 ct
|
| 3.8 mm
|
0.20 ct
|
|
Single Cuts
|
| Diameter
|
Approx. Weight
|
| 1.0 mm
|
0.005 ct
|
| 1.1 mm
|
-
|
| 1.2 mm
|
-
|
| 1.3 mm
|
0.01 ct
|
| 1.4 mm
|
-
|
| 1.5 mm
|
0.015 ct
|
| 1.6 mm
|
-
|
| 1.7 mm
|
0.02 ct
|
| 1.8 mm
|
-
|
| 1.9 mm
|
0.03 ct
|
| 2.0 mm
|
0.035 ct
|
