Diamond Carat Weight Guide

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Of the four C’s, when choosing a diamond carat weight is the element that’s usually most discussed. “How many carats is it?” is one of the most common questions a woman will get asked when showing off her diamond engagement ring. So it’s helpful to understand what is actually meant by the term, and how it can impact the quality, rarity and value of a diamond.


Diamond Carat Meaning Explained

The term ‘carat’ originates from a Greek word meaning “fruit of the carob tree”. Originally, the seeds of the carob pod were used as the standard for measuring diamond weight, as the size of the seeds were almost always identical. Today, the universally understood standard diamond carat weight is 200 milligrams.

Diamond carat refers to the weight of the cut stone, rather than the size.


What are Diamond Points?

A diamond’s carat number is based on a point system where 100 points equates to one carat. This means that a 50 point diamond equates to a half-carat diamond, and so on. The use of the point system means that a diamond can be weighed using exceptionally precise measurements, rather than just whole numbers.


How is Multiple Diamond Jewellery Carats Calculated

Importantly, when there is more than one diamond on a ring, necklace, or other piece of jewellery, such as a three-stone pendant, the stones are weighed together.

The most crucial thing to remember is a large carat weight does not necessarily reflect the size of the diamond. While a diamond may appear bigger, it may weigh less, which means it’s fewer carats.

The weight of the diamond largely influences its price. Larger diamonds are more rare and more desirable, and as such will have a higher cost price. In fact, fewer than one in one million mined stones are large enough to produce a one-carat diamond.

DETERMINING THE SIZE OF A DIAMOND

When it comes to determining how a diamond’s carat weight corresponds to its actual size (or volume), you need to consider the carat in relation to two factors

  1. The dimensions of the diamond’s surface (the crown).
  2. The quality of cut.

The dimensions of the crown refers to the surface area of the top of the diamond. It’s significant because when worn, a diamond is always viewed from the top.

Determining the Quality of a Diamonds Cut

In terms of quality of cut, it’s all about making sure the diamond is not cut too deep or too shallow, as this will impact the size and brilliance of the overall stone. Cut too deep, and some of the carat weight will be hidden in the base, making it appear smaller than it actually is. In turn, if cut too shallow, light will leak through the bottom and the diamond will lose some of its brilliance.

You can find out more about what a diamond cut is with our Diamond Cut Guide here.

CHOOSING THE RIGHT DIAMOND WEIGHT

When choosing the carat of your diamond (also known as diamond weight), you need to take into account the other three C’s, as the overall value of your diamond is dependent on all four factors combined. Additionally, there are a few other things to consider.


Diamond Weight Considerations

When it comes to rings, you need to first examine the size of the finger and determine the size of your desired setting. Large diamonds can sometimes look out of place on delicate fingers, and the setting will largely impact the weight and appearance of the diamond. For example, if you’re clustering diamonds together, you may choose diamonds with a smaller diameter and weight. Some settings can also “swallow” your diamond, which means you’ll have to choose a larger stone for visual appeal.

When it comes to settings, not all diamond shapes and sizes will suit or fit. If you want a particular shape or size, best to choose your diamond first and then choose a setting that suits the stone. If you already have the setting chosen, it’s best to consult with your jeweller.

What is a Good Carat Weight?

Your budget needs to be stretched across the four C’s. For example, if a large carat weight is most important to you, you may then need to choose a diamond of less clarity. It’s best to find a diamond which balances the four C’s, rather than favours one or two components. If you’re unsure of what diamond clarity is or how to measure it then read more in our Diamond Clarity Explained article.

A good tip to remember is diamond prices jump significantly at particular intervals – namely, the half and full-carat weights. Choosing a diamond slightly below those values, for example 0.90-carat, will cost significantly less than a one-carat diamond, when just looking at a price-per-carat basis. And the best thing is, the small size difference will almost be impossible to detect to the naked eye!

Additionally, it’s important to note that two diamonds of the same weight will not necessarily be the same price. The other three C’s – cut, clarity and colour – play equally significant parts as well.

Diamond Carat Weight FAQ’s


How Much Does a 1 Carat Diamond Weigh?

Carat weight is the standard unit of measurement used to weigh diamonds. One carat is equivalent to 200 milligrams, which is 0.2 grams. To put it another way, a carat diamond weighs about the same as a fifth of a gram.


How Weigh a Diamond?

To weigh a loose diamond accurately, you'll need a specialized diamond scale, also known as a carat scale. These scales are highly sensitive and calibrated to measure the tiny increments of weight associated with diamonds, typically down to hundredths or thousandths of a carat. 

  1. Place the loose diamond on the scale's platform, ensuring it's clean and free of any debris that could affect the reading. 
  2. The scale will then display the diamond's weight in carats. 
  3. For mounted diamonds, jewelers often use a "leveridge gauge" which estimates the carat weight based on the stone's dimensions and measurements. However, for the most precise measurement of a mounted diamond, it would ideally need to be removed from its setting and weighed on a carat scale.