Diamond Size Calculator
Round Brilliant
Princess
Emerald
Oval
Marquise
Pear
Cushion
Radiant
Asscher
IF (Internally Flawless)
VVS1 (Very, Very Slightly Included 1)
VVS2 (Very, Very Slightly Included 2)
VS1 (Very Slightly Included 1)
VS2 (Very Slightly Included 2)
SI1 (Slightly Included 1)
SI2 (Slightly Included 2)
I1 (Included 1)
I2 (Included 2)
I3 (Included 3)
D (Colorless)
E (Colorless)
F (Colorless)
G (Near Colorless)
H (Near Colorless)
I (Near Colorless)
J (Near Colorless)
K (Faint Color)
L (Faint Color)
M (Faint Color)
N-Z (Very Light to Light Color)
Estimated Size
Enter details above to see the estimated size.
Understanding Diamond Size: Beyond the Carat
When purchasing or admiring a diamond, its perceived size is a crucial factor, but it's not solely determined by its weight. While carat weight is a primary measure of a diamond's mass, its actual dimensions – its diameter or millimeter measurements – are what dictate how large it appears when viewed from above. This calculator helps estimate the millimeter (mm) size of a diamond based on its carat weight, shape, color, and clarity.
How Diamond Size is Measured
A diamond's size is typically expressed in millimeters (mm) across its top surface (the table facet). This measurement is influenced by several factors:
- Carat Weight: This is the standard unit of weight for gemstones, where 1 carat equals 0.2 grams. All else being equal, a heavier diamond will be larger.
- Diamond Shape: Different shapes distribute their weight differently. For example, a Round Brilliant diamond will appear smaller than an Emerald cut diamond of the same carat weight because the Emerald cut is more elongated and has a larger surface area relative to its weight.
- Cut Quality: The proportions of a diamond (depth and table percentage) significantly impact its appearance. A diamond that is too deep or too shallow can make it look smaller than its carat weight suggests. While this calculator doesn't directly ask for cut parameters, it uses typical ranges for average-to-good cuts for selected shapes.
- Color and Clarity: While primarily affecting a diamond's beauty and value, color and clarity can indirectly influence perceived size. Very high clarity diamonds might have fewer internal obstructions that could break up light, potentially making facets appear larger. Similarly, very faint color might make a diamond appear slightly "larger" in visual impact than a more intensely colored one, though this is a subtle effect.
The Math Behind the Estimation
Estimating a diamond's millimeter size involves using average formulas based on density and typical proportions for each shape. The fundamental relationship is between volume, density, and mass (carat weight). The formula for the volume of a generalized diamond shape can be approximated, and then solved for dimensions (like diameter or length/width) using known average densities for diamond (approximately 3.52 g/cm³).
A simplified approach often involves using empirical data and average ratios for each shape:
- Convert Carat to Grams: 1 carat = 0.2 grams. So,
grams = caratWeight * 0.2. - Calculate Volume: Diamond density is roughly 3.52 g/cm³. Therefore,
Volume (cm³) = grams / 3.52. - Estimate Dimensions: This is the most complex part, as it depends heavily on shape and cut proportions. For round diamonds, a standard formula relates carat weight to diameter. For fancy shapes (non-round), we use average length-to-width ratios and depth percentages that are typical for well-cut stones. These ratios are derived from industry standards and gemological data. For example:
- Round: Formulas often approximate diameter based on carat.
- Princess/Emerald/Asscher (Square/Rectangular): These shapes have length and width. The ratio (e.g., L/W) is key.
- Oval/Marquise/Pear: These are elongated shapes, and their length and width ratios are critical for visual size.
Note: This calculator provides an *estimate*. Actual diamond dimensions can vary significantly based on the precision of the cut, specific proportions (depth, table), and girdle thickness. Factors like color and clarity have a minimal direct impact on physical dimensions but can influence market perception of size for a given weight.
Use Cases for This Calculator
- Comparing Diamonds: Understand how different shapes of the same carat weight will appear visually.
- Budgeting: Get an idea of the physical size you can expect within your budget and preferred shape.
- Educating Yourself: Learn how factors beyond carat weight influence a diamond's apparent size.
- Online Shopping: Cross-reference listings to ensure you understand the dimensions represented by the carat weight.