Diamond carat: price and definition

Whether you are looking for a diamond to mount on a ring, a piece of jewelery or to invest, you are surely wondering:

What is a diamond carat?

This complete article offers you all the explanations on the topic:

1. Definition and explanation of diamond carat weight
2. Evaluation of the carat price of a diamond
3. Measurement, calculation and equivalences between size and carat of diamonds

The diamond carat, a unit of weight used to evaluate the price of the diamond

Fian playsCdiamond wings from the vivalatina collection

Definition of carat for diamonds

One carat corresponds to a weight of 0.2 grams in jewelry.

It is a more precise unit of measurement than grams for measuring the weight of precious stones, especially diamonds.

Historically, the word carat derives from the Arabic word Qirat, carob seed which in ancient times served as a weight reference for weighing gems.

This tree, in fact, produces seeds of very constant weight (between 0.185 and 0.205 grams) and served as a reference standard in the Arab, Greek and Roman world.

Carob, the fruit of the carob tree, produces seeds that in ancient times served as a yardstick to evaluate the weight of the buds

Linguistic explanation of Carat:

We easily notice that all Western languages ​​have the same Greek/Arabic roots, which is why it is called carat:

• in ancient Greek: Keration
• in Arabic: Qirat
• en italien: Carat
• in Spanish: Quilate
• in English: carats

Attention, do not confuse the definition of carat used in jewelry for precious stones and that used in jewelry to evaluate the purity of gold.

In this article we will give you all the useful information on gold carats.

Price in diamond carats

The carat weight of a diamond is just one of the 4 criteria (the famous 4Cs, read here) used to evaluate the price of a diamond.

It is therefore not possible to evaluate the price of a diamond based solely on the criterion of its weight.

To compare the price of two or more diamonds, it is necessary to take into account their quality criteria, that is, compare diamonds of equal quality.

The diamonds most commonly found in jewelry are diamonds of H color and SI clarity, also called HSI.

You should know that the price scale of diamonds is not linear. Since one-carat diamonds are much rarer than 0.5-carat diamonds, their price is higher than that of two 0.5-carat diamonds.

Graph showing the evolution of the price of a carat of HSI diamond as a function of the weight of the diamond considered. This chart is indicative only as it does not detail the cut quality and other variable criteria that influence the price of a diamond.

We must therefore understand that with the same quality, the more we look for a large diamond, the more we will pay for each carat of this diamond.

Therefore, if the price per carat is less than 1,000 euros for a 0.25 carat HSI diamond, it is more than 2,000 euros for a 1 carat HSI diamond and more than 4,000 euros for a 2 carat HSI diamond.

To get an overview (albeit approximate) of the price of a carat of diamond, I invite you to visit this page which offers you an overview.

Table showing the value of a diamond carat in dollars based on color and clarity (missing size and other less common criteria)

How to calculate the carat weight of a diamond?

We can estimate the weight based on the size of the diamond expressed in millimeters or directly measure the weight of a diamond.

To do this it is necessary to use a specific scale, these generally have a precision of around 0.005 carats, which corresponds to one thousandth of a gram.

For the accuracy of the measurement it is therefore necessary to carry out the weighing in a closed space without air movement.

You can easily find this type of carat scales online, here for example.

Precision scale for weighing diamonds in units of carats

Diamond weight expressed in points: 100 points equals 1 carat.

As you know, a 1 carat diamond is relatively large and expensive, so most of the time we work in jewelry with diamonds that weigh less than one carat.

So much so that to express themselves more easily on the subject of small diamonds, jewelers talk about points and no longer carats.

• 1 100 point diamond is equivalent to a 1 carat diamond.
• 1 diamond of 60 points is equivalent to a diamond of 0.6 carats
• 1 10 point diamond is equivalent to a 0.1 carat diamond
• 1 5-point diamond is equivalent to a 0.05-carat diamond

Champagne-colored diamond 3 millimeters in diameter weighing 0.11 carats, or 11 points

Here is a table of correspondences between the size of a diamond in millimeters and its weight in carats expressed in points:

Round Diamond: Conversion of Size in Millimeters to Carat Weight

Note: the weight of a diamond depends on its diameter (taken into consideration here) but also on its size (which affects the height of the diamond and therefore its mass).

Therefore, while these matches are precise for small diamonds, the values ​​are only indicative for diamonds from 2.5 millimeters in diameter.

There will necessarily be deviations of a few hundredths/tenths of a point (tens of milligrams at most) between actually weighed diamonds of a certain size and the corresponding value displayed in this table.

Table showing the correspondence between the size in millimeters of a round diamond and its weight expressed in carats.

Rings in gold and round brilliant cut diamond (photo source)

Princess Diamond: conversion from size in millimeters to weight in carat

Note: The observations on the correspondence between size and weight expressed in the previous table also apply to Princess cut diamonds.

Table showing the correspondence between the size in millimeters of a Princess cut diamond and its weight expressed in carats.

gold ring with princess cut diamond (photo source)

To go further: