Diamond Carat

You can’t always tell the diamond’s size based on carats which is the measure of a diamond’s weight. Carats affect the way diamonds are priced, and the number changes exponentially. In this article, we explain the difference even 0.1 carat can make.


Diamond Carat Weight

The weight of a diamond is referred to in terms of carats (ct). One carat equals 200 milligrams (0.20 grams) and is divided into 100 points for precision. A diamond weighing one tenth of a carat (ct) may be referred to as 0.10 carats or “10-points”.

A diamond’s carat weight is not necessarily reflective of its size. Two diamonds of the same carat weight may appear slightly different in size when viewed from above.

When evaluating the size of a diamond, the top diameter and cut grade must also be taken into account. These are known as the diamond dimensions. The distance across the top of the diamond is crucial, as this is how diamonds are generally viewed once set in jewelry. The cut similarly affects perceived size. A well-proportioned diamond maximizes light, making it appear larger.

Diamond prices tend to jump by half-carats. You will find that the price difference between a 0.9 and 1.0 carat diamond is much larger the difference between a 0.8 and 0.9 ct diamond. Furthermore, diamond prices increase exponentially, rather than linearly. The scarcity of large gem-quality rough diamonds means that a single two ct diamond will cost much more than two one ct diamonds.

TIP: “Carat” (abbreviated ct) is not the same as “karat” (abbreviated K or kt). Carat is measure of gemstone weight while karat is a measure of gold purity.


This carat weight chart describes the carat weight of a diamond and its width in millimetres so it gives you an idea of the ratio of carat weight to physical size.

Diamond Sizes

Frequently Asked Questions

A single carat is 0.2 grams, and a 1-ct diamond will normally have a diameter of approximately 6.5mm. The size of a diamond’s diameter does not increase proportionately with the number of carats.
Prices for half-carat diamonds start at approximately $700 and can rise massively depending on the cut, colour and clarity of the diamond. The most you be likely to pay for the stone alone is about $2,000.
A 1 carat round diamond should measure around 6.5 mm.
There are a lot of factors to take into account which will determine the value of a 1 ct diamond, including the cut, clarity, colour and shape of the stone. Prices currently vary from anything from $1,800 to in excess of $12,000.
A 5 carat diamond weighs approximately 1.0 gram.  
8 Carat diamonds are scarce and prized. You can expect to pay between $12,500 to $40,000 per carat for a diamonds of this size.
The price of a diamond increases with its weight. The Regent Diamond is a carat weight of 140.64 (28.128 g) and owned by the French state and on display in the Louvre, worth $73,920,000 USD. It is considered the most beautiful and purest diamond in the world.
“Carat” (ct) is not the same as “karat” ( K or kt). Carat is a measure of gemstone weight such as diamond carat size, while karat is a measure of gold purity.
Engagement rings vary enormously in cost, so it is impossible to put a figure on them. There are several diamond experts who believe that the man should spend two month’s salary on an engagement ring, while others argue it should be just a month. Probably the best option is to choose an engagement ring that you and your partner will cherish forever.
Most insurance companies will insure engagement rings. However, as they have far more worth than merely monetary value, accurately putting a price on the ring can be a bone of conjecture. Some insurers say that the current market value plus twenty-five per cent is accurate, while others say significantly higher, or frustratingly lower.
The Hope diamond was removed from its setting in 1974 and was found to weigh 45.52 carats, significantly more than the 44.5 carats which it was previously valued at. It is known as an llb diamond and is semi-conductive and phosphoresce.