Gem Weight Estimator, free faceting program written by Gary Kratochvil

Written by Gary Kratochvil
Copyright 2004

The Gem Weight Estimator is a free program written by Gary Kratochvil for the faceting community. The Gem Weight Estimator is a copyrighted program and all rights are reserved by Gary Kratochvil. The current version is 1.2 released on July 26, 2004.

Gem Weight Estimator will calculate the weight in carats of a particular design based on the Volume Factor, width in millimeters, and specific gravity of the material you select. The Volume Factor is calculated by programs such as GemCad. The specific gravity of some materials have a range in values so the estimated weight will also be displayed in a range of carat weights. The program will calculate carat weights from 0.01 to 9,999.99 carats. The input boxes for Volume Factor and Width are designed to only accept numbers and one decimal point. Pressing any other keys will not register within the input boxes.

Gem Weight Estimator is based on the formula:
Weight = (Volume/Widthł) x (Specific Gravity) x (Widthł) / 200

I find the Gem Weight Estimator especially useful in determining which design to use on a particular piece of rough. For example say you have a piece of rough tanzanite from which you can cut an 8 millimeter square stone. The piece has plenty of depth in the rough so several design choices are possible that have similar light return values. The first design has a volume factor of .383 and the second design has a volume factor of .435. Using the Gem Weight Estimator you will find that there will be an approximate difference in the finished weight of the two designs in the amount of .47 carats. If you figure the value of the tanzanite at $300.00 per carat that difference is $141.00! Which design will you use to cut the stone?

Many gemological references do not agree as to the specific gravity value of various materials. The Gem Weight Estimator program will allow you to type in your own values if you choose. In the input box "Select Material Type and Specific Gravity" you can just type in the value you want. The Gem Weight Estimator will calculate a single value for specific gravity or a range of specific gravity values. For example you can enter "3.75" for a single value or "3.75 - 3.85" for a range in values. In the same box you can also start typing the name of the mineral you want to select. If that mineral is in the list the display will automatically jump to that listing. You can also use the drop down arrow and scroll down to the listing of your choice.

In the example below I entered my Volume Factor from GemCad of ".274". Next I entered the width in millimeters of the stone I plan to cut. That measurement was calculated by examining the rough I plan on cutting. The material I am going to cut is tourmaline. When I start typing "tou" in the "Select Material Type and Specific Gravity" box the program jumps to the specific gravity listing for tourmaline. You can also use the drop down arrow and then scroll down to the tourmaline listing. You can also type in the specific gravity value you want to use as mentioned above.

The last thing to do is click the "Calculate" button to get the estimated finished weight of the completed gem.

The accuracy of the Gem Weight Estimator will vary depending on how precisely you cut your stone relative to the planview in GemCad and the accuracy of the specific gravity value of the material you are cutting. The weight of your cut stone will also vary depending on the girdle thickness. The Gem Weight Estimator is a great tool to help you decide which design to use on a particular piece of rough.

Download Gem Weight Estimator by clicking the download icon.

To install the Gem Weight Estimator extract the file "gem_estimator_setup.exe" and the "ReadMe_first.txt" file from the "gem_estimator.zip" file to a directory of your choice. Then double click on the "gem_estimator_setup.exe" file to install. The installation procedure will create a directory for the program, place the Gem Weight Estimator in your Start>Programs, create an uninstall option and place a Shortcut icon on your Desktop. The Gem Weight Estimator runs completely from its own directory. This is a free program and there are no guarantees expressed or implied that this program will run on your system. The program has been tested on Win95, Win98, Win2000 and XP.

Gem Weight Estimator is a copyrighted program written by Gary Kratochvil. All rights are reserved. The distribution of Gem Weight Estimator is only permitted by linking to the Gem Weight Estimator page at www.jewelcutter.com. To email Gary Kratochvil for comments, suggestions or questions use the Contact page.