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The **Carat Weight of a Gem** Calculator accurately estimates the carat weight of a gem based on is 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.

First, choose the gem shape / cut (see diagram). Then, select gem type (see table). Finally, enter the gem's dimension. The calculator will then provide an accurate estimate of the gem's carat weight. The following shapes and cuts are supported:

- Carat Weight of a Round Faceted Gem
- Carat Weight of a Pear or Teardrop shaped gem
- Carat Weight of a Cabochon cut Gem
- Carat Weight of a Cushion Faceted cut Gem
- Carat Weight of a Heart Shaped Faceted cut Gem
- Carat Weight of an Emerald Cut Faceted Gem
- Carat Weight of a Long Rectangular cut Gem
- Carat Weight of a Navette or Boat-shaped Gem
- Carat Weight of a Square Cut Faceted Gem
- Carat Weight of a Marquise Faceted Gem
- Carat Weight of an Oval Faceted Gem
- Carat Weight of a Lozenge Faceted Gem
- Specific Gravity of any Gem based on the type of gem (e.g. Tanzanite).

SUPPORTED TYPES OF GEMS |
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Agate | Alexandrite | Almandite garnet | Amethyst | |

Aquamarine | Beryl | Bloodstone | Blue topaz | |

Carnelian | Cats eye | Chalcedony | Chrysoberyl | |

Citrine | Corundum | Demantoid garnet | Diamond | |

Emerald | Golden beryl | Green beryl | Kunzite | |

Lapis lazuli | Morganite | Onyx | Opal | |

Precious topaz | Pyrope garnet | Quartz | Rose Quartz | |

Ruby | Sapphire | Sardonyx | Smokey quartz | |

Spessartite garnet | Tanzanite (zoisite) | Topaz | Tourmaline | |

Tsavorite garnet | Turquoise | Yellow topaz | Zircon | |

SPECIFIC GRAVITY |

The Carat Weight Calculator has equations 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.

The vCalc Jeweler's calculator is free to use like all the other equations and calculators found in vCalc. Please feel free to comment on this wiki page using the comment button below and help us make a better Jeweler calculator for you.

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.

The 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.

- Jeweler's Calculator - Carat weight estimator for diamonds and other gems, and suite of tools for estimating the value of scrap precious metals.
- Precious Metals Calculator - Near real-time quotes on the SPOT price of Gold, Platinum, Palladium and Silver, with formulas that calculate buy price based on SPOT price, purity (% or karat), refiner's fee and profit (fee).