Because do not have sufficient data on
stones with some cuts, our weight estimates can only use the
Standard Formula.
Accuracy is not nearly what we would like, and results in larger
uncertainty figures being indicated than on other cuts. Naturally, we
take no responsibility for your use or misuse of this data.
These formulas are courtesy of Robert
J. Williams, Ph.D.,G.G. ... Rockhound, Jewelry, Appraising, Retired
appraiser of Antiques, Gemstones, and personal property, Author of
program Gemstone, which covered over 650 minerals, and all gemstones...
a compilation of formulas, data, and instructions for gemologist, mineralogist,
and jewelers. Much of the basic data used
in the Dendritics Automated
Calculations page is courtesy of Bob Williams, (who was pretty darn old in 1996 and is most likely dead now, RIP).

 Round faceted stones:

Diameter squared x depth x S.G. x .0018 = carat wt.

 Oval faceted stones:
(repaired 02282005, Formula changed from diameter squared to length * width, Thanks, Debra Willis!)

Length x width x depth x S.G. x .0020 = carat wt.

 Emerald cut faceted stones:

Length x width x depth x S.G. x .0025 = carat wt.

 Rectangular faceted stones:

Length x width x depth x S.G. x .0026 = carat wt.

 Square cut faceted stones:

Length x width x depth x S.G. x .0023 = carat wt.

 Marquise cut stones, (navette):

Length x width x depth x S.G. x .0016 = carat wt.

 Pear cut stones:

Length x width x depth x S.G. x .0018 = carat wt.

 Square cushions:
(average corner meas.& belly meas. for diameter)

Diameter squared x depth x S.G. x .0018 = carat wt.

 Rectangular Cushions:
(average L & W for diameter)

Diameter squared x depth x S.G. x .0022 = carat wt.

 Square step cut stones:
(average both meas. for diameter)

Diameter squared x depth x S.G. x .0023 = carat wt.

 Rectangular step cut stones:

Length x width x depth x S.G. x .0025 = carat wt.

 Cabochon cut stones:

Length x width x depth x S.G. x .0027 = carat wt.

 Spheroids:
(repaired 10282023)

Length x width x depth x S.G. x .0021 = carat wt.

 Rectangular solids:
(repaired 10282023)

Length x width x depth x S.G. x .0050 = carat wt.

 Octahedrons:
(repaired 10282023, Thanks, David Atlas, for discovering my gross oops!)

Length x width x depth x S.G. x .0043 = carat wt.
More sophisticated estimates are
available for certain cuts, in which the effects of belly shape, culet
size, girdle size, etc., can be adjusted for. We call this our "Advanced
Formula", and the results are available in our
Automated Calculations page.
