How to Weigh a Diamond Using This Diamond Carat Chart

If you’ve recently acquired a diamond, you might be wondering, “how big is my diamond?” While there’s a noticeable difference between a 1/2-carat, 1-carat, and 2-carat diamond, knowing the exact weight of a diamond without a scale can be challenging. This guide will show you a beginner-friendly method for estimating diamond carats. All you’ll need is a millimeter gauge and the chart provided below.

Why We Need Diamond Weight Calculations

Dealers often sell estate jewelry as-is, meaning the diamonds remain in their original settings. In such cases, getting an exact carat weight is difficult because:

  • A scale becomes inaccurate if the jeweler doesn’t remove the gemstones.
  • A closed setting can hide the true diameter of a diamond.
  • Old diamonds have different dimensions than modern cuts.

In these cases, jewelers use a diamond millimeter-to-carat weight calculator to approximate a carat weight. For a quick (and less accurate) estimate, a diamond carat chart can be used.

Diamond Weight Chart

To estimate the carat weight of a diamond:

  1. Measure the diameter of the diamond in millimeters.
  2. Use this measurement in a diamond weight calculator or match it with a carat weight on a diamond weight chart.

The chart below provides an approximate carat weight based on the diamond’s measurements in millimeters. For fancy-shaped diamonds, you’ll need the length and width in millimeters to find an estimated weight.

diamond carat chart

Considerations for Diamond Weight Estimation

This method is applicable to diamonds that are modern calibrated cuts. However, when dealing with antique diamonds, more expertise is required due to factors such as:

  • Girdle thickness
  • Height of the crown
  • Overall depth of the diamond

These factors can significantly impact the diamond’s carat weight and the accuracy of the chart. Also, remember that every gemstone has a different size-to-carat ratio. The chart above will not be accurate for other stones like amethyst or garnet.

More Accurate Carat Weight Calculations

For more precise carat weight calculations, antique dealers use special tools to measure the height of the stone and consider several other factors.

Frequently Asked Questions

We hope this quick and effective beginner method will help you estimate carat weight when shopping for estate jewelry. Here’s a quick summary:

Can I determine the exact carat weight of a diamond without removing it from its setting?

No, it’s difficult to determine the exact carat weight of a diamond without removing it from its setting. The reason for this is that the setting can obscure part of the diamond, making it challenging to accurately measure the dimensions of the stone. Additionally, the metal of the setting can interfere with the weight if you try to weigh the diamond without removing it.

Can I use the diamond carat chart for other gemstones like amethyst or garnet?

No, the diamond carat chart is not accurate for other gemstones. Each gemstone has a different size-to-carat ratio, so a different chart would be needed for each type of gemstone.

What factors can affect the accuracy of the diamond carat chart?

The accuracy of the diamond carat chart can be affected by several factors. For instance, the chart is designed for modern calibrated diamond cuts and may not be as accurate for antique diamonds. The girdle thickness, the height of the crown, and the overall depth of the diamond can significantly impact the diamond’s carat weight and thus the accuracy of the chart. Furthermore, the shape of the diamond (whether it’s a round cut, princess cut, oval cut, etc.) can also influence the accuracy of the weight estimation.

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