How much does a 1 carat diamond cost? A 1 carat diamond ring?
Are you looking for an engagement ring? Wondering how much a 1-carat diamond costs ? A ring with such a stone? What size is it? Miller, the specialist in pre-owned and antique luxury jewelry in Paris, answers all your questions on the subject!
Summary
- Definition of carat
- How much does a 1 carat diamond cost?
- What are the criteria that determine the price of a 1 carat diamond?
- 1 Carat Diamond: Is It Considered a Large Stone? What Is the Actual Size?
- The higher the weight, the higher the price per carat.
- FAQ
Updated September 19, 2025
Definition of carat
A carat is a unit of measurement used in the gemstone industry as a unit of weight . In short, one carat (ct) is equal to 0.2 grams or 200 milligrams. A one-carat diamond therefore weighs one-fifth of a gram.
The first international carat, weighing 205 mg, was proposed in the 1870s. This standard as we know it was created in 1907 at a conference of the International Bureau of Weights and Measures ( BIPM ), located in Paris (Saint-Cloud). It was then quickly adopted internationally. The concept is much older, but the weight of the carat varied from one country to another before standardization.
Also read: Top 9 most expensive rings in the world
How much does a 1 carat diamond cost?
The price of a 1 carat diamond varies considerably from stone to stone . Color, cut, quality... As always when evaluating the value of such a gem, the 4Cs of the diamond will determine its price.
Generally speaking, you can expect to pay anywhere from €1,500 to €15,000 for a high-quality natural 1-carat diamond. The average is around €5,000 per carat for a good-quality natural stone. For a synthetic diamond, it starts around €500 and goes up to €12,000.
And the price of a second-hand 1 carat diamond?
In the diamond industry, there is no such thing as second-hand! This stone is the hardest material known on earth. It does not damage, does not lose its luster... so there is no such thing as a second-hand diamond category.
On the other hand, we obviously make the distinction between new diamond jewelry and second-hand diamond jewelry ! The stone cannot be scratched. On the other hand, the ravages of time can affect a gold ring , a vintage piece of jewelry or platinum earrings with diamond. In this case, you will pay less for your second-hand 1 carat diamond jewelry .
What are the criteria that determine the price of a 1 carat diamond?
In the diamond world, the quality of stones is determined by the so-called 4C system of diamonds. This corresponds to:
- The size (cut)
- The color (color)
- Purity (clarity)
- Weight (carat)
This is why there are such disparities in the prices of 1 carat diamonds .
1 Carat Diamond: Is It Considered a Large Stone? What Is the Actual Size?
A one-carat diamond is already a respectable size in Europe . For example, a standard engagement ring on our continent features a 0.5-carat diamond. Of course, this figure varies depending on one's socioeconomic status.
A 1 carat round-cut diamond results in a stone measuring 6.4 mm in diameter . It is interesting to note, however, that the increase in size is not proportional to the increase in weight. For example:
- A 1.5 carat round diamond has a diameter of 7.3 mm
- 1 round diamond of 2 carats has a diameter of 8 mm
- A 3 carat round diamond has a diameter of 9.2 mm
This is interesting. For example, for a 3-carat stone viewed from above, the diamond's size increases by less than 50% for a weight 3 times greater than a 1-carat diamond !
Additionally, it's important to remember that a carat is a unit of weight. The size (shape) of a diamond will have a significant impact on its volume, whether real or perceived. For example, a 1-carat princess-cut diamond will be more compact than a pear- or oval-cut diamond of equal weight.
It's also important to remember that, for example, when choosing a diamond ring , the size of the wearer's hands will have an impact. The smaller the hands, the more imposing the 1-carat diamond will look! To make the right purchase, see our guide " How to choose a diamond ring ."
The higher the weight, the higher the price per carat.
For a one-carat diamond, the price caps around €15,000. However, for a stone of a similar quality with a higher mass, this price per carat will increase significantly. A larger stone will therefore be more expensive on two counts (intrinsic mass + increase in price per carat ).
The world's most valuable diamonds cost millions per carat . For example, the Oppenheimer Blue sold for $3.93 million per carat. The Williamson Pink Star diamond sold for $4.475 million per carat. These two exceptional gems are among the top 10 most expensive diamonds in the world .
Price per carat of diamonds (natural)
| Weight | Diamond Price (Average) | Price of a used ring (APD) |
| 1/2 carat | Around €1,500 | Around €3,500 |
| 1 carat | Around €5,000 | Around €7,000 |
| 1.5 carats | Around €9,000 | Around €12,000 |
FAQ 1 carat diamond price
The price range is similar to that of diamonds in general, so let's say from €1,500 to €15,000.
1 carat synthetic diamonds tend to be less expensive for similar quality. They can be found for as little as €500.
At Miller, you can find such luxury rings for around €6,000-8,000.
