Gemstone Carat Weight Calculator

The Gemstone Carat Weight Calculator estimates the carat weight of a gem based on its shape (see diagram), dimensions and the type of gem (e.g. ruby).  The type of gem is used to look up the specific gravity of the gem which is combined with the approximate volumetric size to compute the carat weight.  

INSTRUCTION:

1. First, choose the gem shape / cut (see diagram).  
2. Click on the calculator button indicating that shape (e.g., Cabochon Cut)
3. Select gem type from the displayed calculator menu.  
4. Enter the gem's dimension.  

The calculator returns an accurate estimate of the gem's carat weight.  

Gemstone Carat Weight Calculator:

• Weight Estimate of a Round Faceted Gem
• Weight Estimate of a Pear shaped or Teardrop Gem
• Weight Estimate of a Cabochon Cut Gem
• Weight Estimate of a Cushion Faceted Gem
• Weight Estimate of a Heart Shaped Gem
• Weight Estimate of an Emerald Cut Faceted Gem
• Weight Estimate of a Navette Cut Gem
• Weight Estimate of Long Rectangular Cut Gem
• Weight Estimate of Square Cut Faceted Gem
• Weight Estimate of Marquise Faceted Gem
• Weight Estimate of an Oval Faceted Gem
• Weight Estimate of Lozenge Faceted Cut Gem

Types of Gems

The gems supported in gemstone carat weight calculator include the following:

Agate, Alexandrite, Almandite garnet, Amethyst, Andalusite, Aquamarine, Aventurine, Beryl, Bloodstone, Blue Topaz, Carnelian, Cats eye, Chalcedony, Chrysoberyl, Citrine, Corundum, Demantoid Garnet, Diamond, Emerald, Golden beryl, Green beryl, Jadeite, Kunzite, Lapis Lazuli, Morganite, Nephrite Jade, Onyx, Opal, Precious topaz, Pyrope garnet, Quartz, Rhodolite garnet, Rose Quartz, Ruby, Sapphire, Sardonyx, Smokey quartz, Spessartite garnet, Spinel, Tanzanite, Topaz, Tourmaline, Tsavorite garnet, Turquoise, Yellow topaz, Zircon

The Gemstone Carat Weight Calculator has functions and data useful for Jewelers and other merchants of gems.  The equations for gems (including diamonds) provide the approximate carat weight of a gem based on its shape and dimensions.  These equations approximate the volume of the gem and use the specific gravity to provide a karat weight estimate.  The different weight approximations are based on the shape of the gem (see list of cuts below). 

The gem cuts include: round (circular), oval, emerald cut, long rectangular, square, navette or boat-shaped, pear-shaped or teardrop, cabochon, princess cut, Cushion cut, Old European cut and Lozenge Faceted.

NOTE: Never use an estimating equation for the weight of a gem if you can weigh it on a quality jeweler's scale.  These equations are useful when the jeweler is trying to preserve the setting of the gem while still providing a carat weight estimate.  In this way, the jeweler can ascertain the type of gem, its shape and then using precise measuring tools measure the salient dimensions for use in these equations.  These steps can be done while the gem remains in the setting.

APPLICATIONS

This calculator provides Jewelers and other merchants of gems and precious metals to compute an estimated current market value for jewelry items.  Likewise private owners and insurance providers can make similar estimates for use in establishing the basis for insurance valuation and coverage.

ACCURACY COMPARISON

The carat weight equations and data used in vCalc's jewelry library and calculator were reviewed by a certified gemologist.   The equations are based on industry recognized formulas and data.  The table below shows a comparison of computations between vCalc and an industry accepted application (Quantum Leap).

The length, width and depth are in millimeters (mm), and the Quantum Leap and vCalc measurements are in carats (cwt).

The largest variance, an oval faceted alexandrite, which can be seen in the last row above, has been double checked against several source equations which tend to support vCalc's accuracy.