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Diamond Measurements: All You Need To Know Before You Buy

Diamond Measurements

Diamonds should sparkle. Display fire from afar. Radiate under different kinds of light. Be big enough to gleam and catch everyone’s eye. This is what most of us expect from diamonds.

To ensure this, what factors do you consider when choosing diamonds? Is it size or diamond carat and sparkle? Most people only consider these aspects.

But when it comes to diamonds—mined or lab grown diamonds—there’s more than meets the eye. Many more aspects make or break its performance.

And so, when you miss assessing all the important factors, you bring home a poor quality diamond that doesn’t doesn’t sparkle, looks dull, loses its sheen, and displays poor performance far from your expectations.

And that’s why we wrote this article—for you to understand what factors to consider and how to make an informed decision when buying diamonds.

Why to measure diamonds?

Measuring a diamond is important for many reasons. Let’s look at some of them:

How to understand the different diamond measurements? 

Carat or size

To begin with, the size and carat of diamonds are two different things, but many confuse it as the same. 

Diamond carat is the weight. Each carat is equal to 0.2 grams, therefore, a five-carat diamond weighs one gram. Whereas, diamond size is how large the diamond will look when seen from above. 

Diamond sizes are measured in millimeters (mm). A one carat diamond is typically 6.5 mm. The important thing to note is that the size and carat of diamonds changes with the shape of the diamond. 

The size and carat of diamonds is a key factor that helps determine its price. For example a 1 carat diamond cost would be lesser than a 1.5 carat diamond price.

Length to width ratio

Another aspect to measure is the length to width ratio of diamonds. It is calculated by dividing the diamond’s length by its width. It helps understand the proportions of a diamond. It is most relevant for diamonds shaped oval, square, rectangle, etc. 

Every diamond shape has a range of ideal length to width ratio, as mentioned below:


To measure diamond color, you have to measure the absence of any tint or hue. In the world of diamonds, the more colorless a stone is, the better its quality grade.

The GIA’s diamond grading method measures the colourlessness of diamonds on a scale from D to Z, D being colorless and the best, and Z are diamonds that have visible colors.

The color differences in diamonds are subtle and may not be visible to the naked eye. Diamonds have to be assessed in laboratories by experts.


The most attractive factor about diamonds is its shine or sparkle. And that’s where assessing the diamond cut comes in. How does cut impact diamond sparkle? Light falls on the diamond and reflects back, and that’s what causes diamonds to sparkle.

Of all the factors, cut is the most complex diamond measurement. The process involves evaluating the internal and external light reflection. Gemologists assess the way white light falls and forms patterns and sparkles due to the reflection.


Another of the 4Cs is clarity. Diamonds can contain impurities, marks, imperfections and inclusions. These factors impact the diamond’s clarity grading. In short, the less imperfections and inclusions, the better its clarity.

Final thoughts

Measuring diamonds is one of the most critical steps to ensure customers buy their gemstones with complete knowledge. It helps determine the quality and price of diamonds. So the next time you’re looking for a diamond, this short guide will help you make informed choices based on diamond measurements.

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