Diamond Carat Weight

Diamond Education › Carat Weight

Diamond Carat Weight — Size, Weight & Value

Carat is the unit of weight used to measure diamonds. One carat equals 0.2 grams, or 200 milligrams. While carat weight has a significant impact on a diamond's price, it's one of the most misunderstood of the 4Cs — because carat measures weight, not size.

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Carat Weight vs Actual Size

Two diamonds of exactly the same carat weight can look very different in size. This is because size depends on how the diamond is cut — specifically its proportions and the distribution of weight between the crown (top) and pavilion (bottom).

A deep-cut diamond carries most of its weight in the pavilion below the girdle. It may weigh 1.00ct but appear noticeably smaller on the finger than a well-proportioned 0.90ct diamond where the weight is distributed to maximise the face-up diameter.

This is one of the most important reasons why cut quality matters so much — and why at Diamond Imports, we focus on cut first.

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Approximate Measurements by Carat Weight

For round brilliant diamonds, approximate face-up diameters are:

Carat Weight	Approx. Diameter (Round Brilliant)
0.50ct	5.2mm
0.75ct	5.9mm
1.00ct	6.5mm
1.25ct	6.9mm
1.50ct	7.4mm
2.00ct	8.2mm
3.00ct	9.4mm

Note: these are approximate measurements for well-proportioned stones. Actual measurements will vary based on cut.

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Magic Weights and Price Steps

Diamond prices increase significantly at certain carat weights — known as magic weights or threshold weights. These are typically:

• 0.50ct
• 0.75ct
• 1.00ct
• 1.50ct
• 2.00ct
• 3.00ct

A 0.99ct diamond is significantly less expensive than a 1.00ct diamond of identical quality — yet looks virtually identical on the finger. Similarly, a 0.96ct diamond may offer outstanding value compared to a 1.00ct stone, with almost no visible difference in appearance.

Understanding magic weights allows savvy buyers to get more diamond for their money. At Diamond Imports, Daniel will always highlight these opportunities when they exist in his stock.

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How Carat Affects Price

Diamond prices do not increase linearly with carat weight — they increase exponentially. A 2.00ct diamond is not twice the price of a 1.00ct diamond of the same quality — it is typically three to four times the price, because larger diamonds are significantly rarer.

This is why balancing the 4Cs is so important. For a given budget, you might choose between:

• A larger diamond with slightly lower colour or clarity
• A smaller diamond with exceptional cut, colour, and clarity

There's no single right answer — it depends entirely on what matters most to you and the person wearing the diamond.

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Fancy Shapes and Visual Size

For the same carat weight, some diamond shapes appear larger than others due to their proportions:

• Oval, marquise, pear, and emerald cuts often appear larger than round brilliants of the same carat weight, because their elongated shape distributes weight across a larger surface area.
• Round brilliant cuts are the most brilliant but appear slightly smaller face-up than elongated shapes of the same weight.

This is worth considering if appearance size is important to you.

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