How much does a 1 carat diamond cost? A 1 carat diamond ring?
Are you looking for an engagement ring? Wondering what the price of a 1-carat diamond is? What about a ring with such a stone? How big is it? Miller, the specialist in luxury and vintage jewelry in Paris, answers all your questions on the subject!
Table of Contents
- Definition of Carat
- What is the Price of a 1-Carat Diamond?
- What Criteria Determine the Price of a 1-Carat Diamond?
- 1-Carat Diamond: Is it Considered a Big Stone? What is the Actual Size?
- The Higher the Weight, the More Important the Price per Carat
- FAQ
Updated on September 19, 2025
Definition of Carat
The carat is a unit of measurement used in the precious stones industry as a unit of weight. In short, one carat (ct) is equivalent to 0.2 grams or 200 milligrams. Therefore, a 1-carat diamond weighs one-fifth of a gram.
The first international carat, weighing 205 mg, was proposed in the 1870s. The standard we know today was created in 1907 at a conference of the International Bureau of Weights and Measures (BIPM), located in Paris (Saint-Cloud). It was quickly adopted internationally. The concept is much older, but the weight of the carat varied from country to country before standardization.
Also read: Top 9 Most Expensive Engagement Rings in the World
What is the Price of a 1-Carat Diamond?
The price of a 1-carat diamond can vary significantly from one stone to another. Color, cut, quality... As with any gemstone valuation, the 4Cs of a diamond will determine its price.
Generally, you can expect to pay from around $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 diamond. For a synthetic diamond, prices start around $500 and can go up to $12,000.
What is the Price of a 1-Carat Diamond (Pre-Owned)?
In the diamond industry, there is no real concept of "second-hand"! This stone is the hardest known material on Earth. It does not get damaged, does not lose its luster... so there is no category for pre-owned diamonds.
However, there is a distinction between new diamond jewelry and pre-owned diamond jewelry! The stone itself cannot be scratched. However, the ravages of time can affect a gold ring, a vintage piece, or diamond earrings. In this case, you will pay less for a pre-owned diamond ring.
What Criteria Determine the Price of a 1-Carat Diamond?
In the diamond world, the quality of stones is determined by the system known as the 4Cs of a diamond. This includes:
- Cut
- Color
- Clarity
- Carat weight
This is why there are such disparities in the prices of 1-carat diamonds.
1-Carat Diamond: Is it Considered a Big Stone? What is the Actual Size?
A 1-carat diamond is already a respectable size in Europe. For example, on our continent, a standard engagement ring features a 0.5-carat diamond. Of course, this figure varies depending on socio-economic categories.
A 1-carat round diamond measures 6.4 mm in diameter. However, it is interesting to note 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
- A 2-carat round diamond 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 size of the diamond increases by less than 50% for a weight three times that of a 1-carat diamond!
Additionally, it is important to remember that the carat is a unit of weight. The cut (shape) of the diamond will significantly impact its volume, both real and perceived. For example, a 1-carat princess-cut diamond will be more compact than a 1-carat pear or oval-cut diamond.
It is also important to note that in the case of a diamond ring, for example, the size of the wearer's hands will have an impact. The smaller the hands, the more imposing a 1-carat diamond will appear! For a good purchase, see our guide "How to Choose a Diamond Ring".
The Higher the Weight, the More Important the Price per Carat
For a 1-carat diamond, the price caps around $15,000. However, for a stone of similar quality but greater weight, the price per carat will increase significantly. A larger stone will therefore be more expensive for two reasons (intrinsic weight + increase in price per carat).
The most valuable diamonds in the world cost several million dollars per carat. For example, the Oppenheimer Blue sold for $3.93 million per carat. The Williamson Pink Star 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 Natural Diamonds
| Weight | Average Diamond Price | Average Price of a Pre-Owned Ring (APD) |
| 1/2 carat | Approx. $1,500 | Approx. $3,500 |
| 1 carat | Approx. $5,000 | Approx. $7,000 |
| 1.5 carats | Approx. $9,000 | Approx. $12,000 |
FAQ on 1-Carat Diamond Prices
The price range is similar to that of diamonds in general, so around $1,500 to $15,000.
Synthetic 1-carat diamonds tend to be less expensive for similar quality. They can be found starting at around $500.
At Miller, you can find such luxury rings for around $6,000 to $8,000.
