Diamond Carat
Understanding diamond quality is simplified by considering carat weight, which refers to the diamond’s weight. It's important to note that carat weight doesn't precisely reflect the diamond's size. Some shapes may appear larger despite having the same carat weight; for instance, the Marquise diamond is known for optimizing carat weight. Learn more below.
In short: One diamond carat equals 200 milligrams (0.2 grams) — a unit of weight, not size. Diameter scales gradually: a 0.50ct round brilliant measures ~5.2mm across, 1.00ct ~6.5mm, 2.00ct ~8.2mm. US retailers price diamonds in per-carat bands (0.50ct, 0.70ct, 1.00ct, 1.50ct) with sharp jumps at each threshold. Buying just under a threshold (e.g. 0.95ct) typically saves 10-20% at near-identical face-up size.
The term "carat" is widely used in jewelry, while "karat" denotes the purity of gold, so it's crucial not to confuse the two. Carat is a unit of weight, often represented as ct. One carat equals 200 milligrams, with carats further divided into points, where one point is 0.01 carat, equivalent to two milligrams. The UK officially adopted "carat" as the measurement for diamonds in 1914, now a standardized global measurement.
In addition to cut, color, and clarity, carat weight is a key factor influencing a diamond's price. Generally, heavier diamonds are more expensive and scarcer. However, it's essential to remember that heavier doesn't necessarily mean larger; the cut and shape of the diamond also play a crucial role and should be carefully considered.
On the hand
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Carat is denoted by ‘ct’
1 carat = 0.2 grams
5 carats = 1.0 gram
The term "carat" originates from the carob or locust tree (Ceratonia siliqua) in Mediterranean lands. Traders once used the dried seeds of this tree as a consistent unit of weight for gems, each seed weighing around 1/5 gram.
When buying, consider aiming for a carat weight just below popular weights like 1 ct. and ½ ct. This can often result in a slightly lower price, as the diamond falls just short of the popular carat weight.
Oversizes may trade at premiums of 5% to 15% over similar quality straight sizes.
Oversizes are: (0.60-0.69), (0.80-0.89), (0.96-0.99), (1.30-1.49), (1.75-1.99), (2.50+), (3.50+), and (5.50+)
Diamond carat: frequently asked questions
What is a carat?
A carat is a unit of weight, not size — one carat equals 0.2 grams (200 milligrams). It is written as ct.
Is carat the same as a diamond’s size?
Closely related but not identical. Two diamonds of the same carat can look different sizes depending on their cut and shape — elongated shapes such as oval or marquise tend to look larger for their weight.
What carat weight should I choose?
It depends on budget and the wearer’s hand. One to 1.5ct is the most popular range. A useful tip: buying just under a round number (say 0.90ct instead of 1.00ct) can save money for a size difference no one will notice.
Why does price jump at 1 carat and 2 carats?
Prices rise sharply at these “magic sizes” because demand clusters there and larger rough is rarer. Sitting just below a magic size is one of the easiest ways to save.
Does carat affect price the most?
Carat drives price the fastest of the 4Cs, and the rise is steep rather than linear — a 2ct diamond costs far more than twice a 1ct of the same quality.
