Carat Calculator

Diamond Carat Weight Estimator

Use this calculator to estimate the carat weight of a diamond based on its measured dimensions (length, width, and depth) and shape. This tool is particularly useful for estimating the weight of mounted diamonds or loose stones when a precise scale is not available.

Round Brilliant Princess Emerald Oval Pear Marquise Heart Radiant Asscher Cushion

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Understanding Diamond Carat Weight

The term "carat" refers to the standard unit of weight for diamonds and other gemstones. One carat is precisely defined as 200 milligrams (0.2 grams). It's important to note that carat is a measure of weight, not size, although a heavier diamond will generally appear larger.

Why Estimate Carat from Dimensions?

Estimating a diamond's carat weight from its dimensions is a common practice, especially when the stone is already set in jewelry, making direct weighing difficult or impossible without removing it. Jewelers and appraisers often use this method for quick assessments or when dealing with loose stones where a precise scale isn't immediately available. The calculation relies on the diamond's specific gravity (density) and its geometric shape.

How the Calculator Works

Our calculator uses a widely accepted formula to estimate carat weight: Length (mm) × Width (mm) × Depth (mm) × Factor. The 'Factor' is a constant that varies significantly based on the diamond's shape. This is because different shapes have different proportions and distributions of mass. For instance, a round brilliant diamond with the same length and width as a princess cut will have a different depth percentage and thus a different weight for the same face-up appearance.

The Role of Diamond Shape

Each diamond shape has a unique set of ideal proportions, which influences how its weight is distributed. For example:

• Round Brilliant: Often considered the most brilliant, its factor accounts for its specific depth-to-diameter ratio.
• Princess Cut: A square or rectangular shape, its factor reflects its typically deeper pavilion.
• Emerald Cut: A rectangular step-cut, its factor is higher due to its larger table and shallower depth relative to its length and width.
• Other Shapes (Oval, Pear, Marquise, Heart, Radiant, Asscher, Cushion): Each has a unique factor derived from its typical proportions and how its weight is distributed across its dimensions.

Limitations of Carat Estimation

While this calculator provides a useful estimate, it's crucial to understand its limitations:

• Approximation: The factors used are averages based on ideal or common proportions. Actual diamonds can vary significantly in their cut quality, girdle thickness, culet size, and overall depth percentage, leading to deviations from the estimated weight.
• Specific Gravity: The calculation assumes a standard specific gravity for diamond (approximately 3.52). However, slight variations can occur.
• Measurement Accuracy: The accuracy of the estimate heavily depends on the precision of your length, width, and depth measurements. Even a fraction of a millimeter can alter the result.
• Not a Substitute for Professional Weighing: For certified appraisals or sales, an actual carat weight obtained from a calibrated jeweler's scale is always required.

Examples of Carat Estimation:

• Round Brilliant: A diamond measuring 6.5mm (Length) x 6.5mm (Width) x 3.9mm (Depth) would estimate to approximately 1.00 carat. (6.5 * 6.5 * 3.9 * 0.0061 = 1.00 ct)
• Princess Cut: A diamond measuring 5.0mm (Length) x 5.0mm (Width) x 3.5mm (Depth) would estimate to approximately 0.73 carats. (5.0 * 5.0 * 3.5 * 0.0083 = 0.73 ct)
• Emerald Cut: A diamond measuring 7.0mm (Length) x 5.0mm (Width) x 3.0mm (Depth) would estimate to approximately 0.97 carats. (7.0 * 5.0 * 3.0 * 0.0092 = 0.97 ct)

This Carat Weight Estimator is a handy tool for quick reference, helping you get a general idea of a diamond's weight based on its visible dimensions and shape.