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 "cents." 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 - .59 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 8 .125 ct 1/8 10 .10 ct 1/10 33 .03 ct 1/33 50 .02 ct 1/50 70 .015 ct 1/70 100 .01 ct 1/100 125 .008 ct 1/125 150 .007 ct 1/150 200 .005 ct 1/200   Estimating Melee Weights By Diameter: Full Cuts Diameter Approx. 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 Avg. Weight Range 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