Diamond carat

What is diamond carat?

Carat is the unit of measurement for the physical weight of diamonds. It is measured using a highly accurate digital scale, with one carat equaling .20 grams.

Diamond carat measures the weight of a stone, but this does not mean its size. This is because two stones that look like the same size could have different weights, for instance if one of the stones has a deeper cut - meaning there is more diamond below the top surface of the stone. Similarly, varying diamond shapes of the same weight can look like different sizes based on its surface dimension compared to its depth.

Certain settings can also make a diamond look larger, for example our classic halo setting achieves this by having a ‘halo’ of small lab-grown diamonds around the larger center stone, enhancing the visual impact of the central lab-grown diamond.

Another area of confusion is that a larger carat weight is always ‘better’ than a smaller carat, when carat weight is not related to sparkle. A bright, brilliant diamond is the result of excellent clarity combined with precision cutting to maximize the amount of light that hits the facets of the stone. This applies no matter the carat weight, and is what gives even the smallest diamonds their signature, and singular, sparkle.


About diamond carat pricing

Diamonds with a large carat weight, combined with a high grade of cut, clarity and color see a exponential price increase due to their rarity. In nature, diamonds with higher carat weights are cut from larger rough crystals that are harder to source than their smaller counterparts, making them rare. 

These larger crystals become even rarer in combination with the other 4 c’s; a colorless stone with only minor inclusions that will lead to an excellent clarity when cut.

This is where natural diamonds and lightbox lab-grown diamonds differ. Because each batch of our lab-grown diamonds is produced to the same standard of cut, color and clarity, our carat weight is linear; always 800 USD a carat. By removing ‘rarity’ as a pricing factor, our stones become more affordable, even for our larger carat weights. 

What does total carat weight mean?

Total carat weight is the measured weight of all the diamonds in any given piece combined. Any time you see ct.tw after a number in our product descriptions, this refers to the total weight of the combined lab-grown diamonds in one of our pieces. The individual weight of all the lab-grown diamonds included is then listed separately in the product description.

  • Our environmental commitment

    At Lightbox we are big on transparency and our commitment to reducing the footprint of our stones is a huge part of this. See more on how we grow our stones with 100% renewable energy.

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  • Visit the lab

    Explore the Lightbox Lab in Portland, Oregon, home to our world-leading technology producing up to 200,000 carats a year, each one always VS clarity, very good cut and now 'grown in the USA'.

  • Lab-grown FAQs, answered.

    Our leading technology means our lab-grown diamonds are among the highest quality you can find. Learn more about the science behind the sparkle with our guide to lab-grown diamonds.