Diamond Carat Meaning: Chart, Size, Weight Explained


A $50 – $100 million diamond heist at Brussels Airport in Belgium 2013 is the biggest and one of the most memorable modern inside jobs that even made Hollywood take notice by releasing a movie based on the robbery of this spectacular diamond heist.

The fascination for sparkling gemstones can either lead some to rob a departing plane full of precious gemstones. Or like you and me, hopefully, just to legally buy lustrous diamond jewelry after understanding carat meaning, size, weight, and so on intimately.

A carat (ct) is a mass unit of measuring natural diamonds and equals 200 grams (0.200) or ⅕ gram which is subdivided into 100 points. The metric carat word is derived from Greek kerátion (carob tree seed), a unit of weight back then. Every diamond under 1 carat is defined in points and vice versa.

Diamond Carat Explained

The best way to fully understand the meaning of diamond carat weight is to put it in relation to other commonly used measurements in our daily lives, for example, carat vs size by diamond cut.

Diamond Carat Chart

Cut Type | Carat→ 0.25 mg 0.50 mg 0.75 mg 1 mg 1.5 mg 2 mg 3 mg
Round 4.1 mm 5.1 mm 5.8 mm 6.4 mm 7.4 mm 8.1 mm 9.3 mm
Princess 3.5 mm 4.4 mm 5 mm 5.5 mm 6.4 mm 7 mm 8 mm
Marquise 6.5*3mm 8.5*4 mm 9.5*4.5 mm 10.5*5 mm 12*6 mm 13*6.5 14*7mm
Cushion 4*3.5 mm 5*4.5 mm 6*5 mm 6.5*5mm 7.5*5 mm 8*7 mm 9*8 mm
Emerald 4.5*3 mm 5.5*4mm 6*4.5 mm 6.5*5mm 7.5*5.5 mm 8.5*6mm 9.5*7mm
Radiant 3.5*3mm 5*4.5 mm 5.5*5mm 6*5.5 mm 7*6 mm 7.5*7mm 8.5*7.5mm
Pear 5.5*3.5mm 7*4.5 mm 8*5 mm 8.5*5.5 mm 10*6.5 mm 10.5*7mm 12.5*8 mm
Oval 5*3 mm 6*4 mm 7.5*5mm 8*5.5 mm 9*6 mm 10.5*7mm 11.5*7.5mm
Asscher 3.7 mm 4.4 mm 5 mm 5.5 mm 6.4 mm 7 mm 8.1 mm
Heart 4.2 mm 5.4 mm 6.0 mm 6.7 mm 7.6 mm 8.3 mm 9.5 mm

The Diamond Cut Process

The diamond’s standardized carat weight is measured in grams (mg), e.g. 1 carat (1 mg). 

Since rough natural diamonds are cut into different types of shapes to fit commercial desire, e.g. the popular round brilliant cut. This way they eventually end with different sizes, depending on their diamond cut.

Diamond Carat Buying Guide

  • Example 1: Carat vs Size (Round Brilliant Diamond Engagement Ring)

Looking at the diamond carat chart for example, 1 mg carat round diamond equals 6.4 mm size

  • Example 2: Carat vs Size (Emerald Diamond Earrings)

A 0.25 mg weighing emerald diamond carat equals 4.5*3 mm in size. 

  • Example 3: Carat vs Size (Heart Diamond Pendant)

A 9.5 mm sized heart diamond cut possesses 3 mg carat weight.

Note: All the carats are weighed using an electronic scale for diamonds. Nevertheless, diamond sizes as described on a diamond carat chart are close estimates as no diamond is the same. Therefore, no measuring is 100% 1:1.

This chart is a simple and effective diamond buying guide taking the carat weight, diamond size, and diamond-cut into consideration from shinning crystal rings to stunning diamond bead strands and other types of diamond-based jewelry.

Certainly it will make it easy for a guy to get a yes even if his best promise ring vow for her wasn´t perfect, if the diamond jewelry size, cut, and carat are,

Carat Weight And Four Cs

Next to these factors (carat, weight, and cut), when buying a diamond you always have to include the 4 C´s (cut, clarity, color, and carat weight) in order to evaluate the true value of any real diamond.  Respectively stimulants too, whereby generally bigger is not necessarily better.

In other words, one single 2 mg cushion cut diamond is maybe more valuable than two single 1 mg cushion diamond cut.

Moreover, since other grading factors from color to clarity (4 C´s of a diamond), play a significant role in diamond jewelry determination of quality and price, two equal carat stones may be of different value.

The reason for the different evaluation for an otherwise same carat or equal size diamond gems may be furthermore the fact that large-sized unpolished stones are naturally rare, therefore a huge paragon (99.999% flawless diamond, no blemishes) is high-valued, expensive.

Atom-level grading of diamond quality ain’t an easy research undertaking by any means and can only go so far regarding resources, technology, and time.

Another aspect to consider before buying a brilliant is that a 1-carat round cut diamond earring for example is usually set in 14K rose gold or similar.

Meaning, you don’t pay simply for a loose diamond, but for a brilliant gold jewelry set whereby the 14K gold carries its very own value in dollars and perceived worth.

Carat vs Karat

Carat (ct) with a C is a diamond unit weight for measuring a gemstone whereas karat (k) with a K is a mass unit for measuring real gold. This is true in the United States of America and other jurisdictions, however, be aware in some countries’ carat with C is used for both diamond and gold units.

Diamond Carat Definition (Conclusion)

Measuring the diamond’s weight by carat unit is the international standard of all jewelers and consumers purchasing fancy diamond bead strands, sparkling necklaces, and white round brilliant rings.

Beyond this important factor though, we have discovered the world of the other C´s in diamonds. Next to diamond carat meaning – things like color, clarity, and cut and their essential role in determining the final perceived value and price of polished diamonds.

Note: Lab-created diamonds are also weighed by carat, however since these are diamond simulants they are a fraction of the price of real diamonds whereby they share many similar properties, albeit not as valuable as polished natural stones.

Now you are hopefully ready and equipped with the knowledge of an informed diamond shopper.

Maybe you can even at least help the authorities next time in detecting the lost loose diamonds, as in the infamous Belgian diamond heist where only a fraction has been recovered so far.

More jewelry diamond knowledge before you shop for your favorite engagement or promise ring below.

Which Carat Diamond Is Best?

Diamond carat weight of 0.5 mg is currently quite popular for couples. A round brilliant half-carat diamond engagement ring can cost around $1,000. This represents the lower end of real diamond rings and in terms of cut, clarity, and color (the 4 C´s) is a great deal, also as a princess cut for her.

How Much Is A Diamond Carat Worth?

A 1 mg carat diamond is typically worth $2,000 up to $20,000 or more depending on the cut, color, clarity, and of course the carat weight (four C´s). Moreover, everything under 1 carat is relatively lower priced than diamonds 1 carat (ct) above. Under 1ct diamonds are measured in points only.

How Can You Tell A Diamond Is Real?

When a diamond drops to the bottom of a bowl or glass of water, it’s 99.99% real diamond, but when the jewelry float or is atop, then it’s a fake one. The reason is due to higher density of 3.5–3.53 g/cm3 compared to water 9.97e+8 (g/cm3). Therefore, diamond water test can tell if a diamond is real.

Bill Dominic

Bill is an art history and business graduate. Moreover, he loves to test, compare, shop jewelry & fashion items for his 5 sisters, girlfriend, nieces when not enjoying a great novel.

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