Diamond Carat
Understanding diamond weight, how it affects price, and why bigger isn't always better.
Understanding Diamond Carat
Carat is the standard unit of weight for diamonds and gemstones. One carat equals exactly 200 milligrams (0.2 grams). The word "carat" originates from the carob seed — ancient gem traders used these remarkably uniform seeds as counterweights on their balance scales because each seed was almost identical in mass.
Key insight: Prices jump significantly at "magic numbers" — 0.50ct, 1.00ct, 1.50ct and 2.00ct. A 0.95ct diamond looks virtually identical to a 1.00ct diamond but can cost 15–20% less.
Today, the metric carat is internationally standardised by the General Conference on Weights and Measures. Every certified diamond is weighed to the hundredth of a carat (two decimal places) using highly sensitive electronic scales. A diamond weighing 1.38 carats, for example, is described as "one point three eight carats" — or simply "one thirty-eight" in diamond trade parlance.
Carat Weight & Face-Up Size
While carat measures weight, the table below shows how different carat weights translate to visible face-up diameter for a round brilliant diamond with ideal proportions. These circles are drawn to scale.
Carat Weight Reference Guide
The following table provides a comprehensive overview of common carat weights, their approximate face-up dimensions, and practical size references to help you visualise each weight.
*Approximate diameters for round brilliant cut with ideal proportions. Fancy shapes will vary.
Carat Weight & Price
Diamond prices increase exponentially, not linearly, with carat weight. A 2-carat diamond doesn't cost twice as much as a 1-carat diamond — it can cost 4 to 5 times more. The reason is simple: larger rough diamonds are significantly rarer in nature, making them disproportionately valuable.
This exponential pricing curve means that buying just below a magic number is one of the smartest strategies for diamond buyers. A 0.90ct diamond and a 1.00ct diamond are virtually indistinguishable face-up, yet the price difference can be dramati
Understanding Magic Numbers
In the diamond trade, certain carat weights are known as "magic numbers" — the psychological thresholds where consumer demand (and therefore prices) spike dramatically. These are 0.50ct, 1.00ct, 1.50ct and 2.00ct.
The price jumps occur because diamond cutters are incentivised to keep stones above these thresholds. A rough diamond that could produce a beautifully proportioned 0.95ct stone might instead be cut to a mediocre 1.01ct — sacrificing cut quality to hit the magic number. This is why it's crucial to always prioritise cut grade over carat weight.
Smart buying tip: Look for diamonds in the "sweet spot" ranges: 0.40–0.49ct, 0.85–0.99ct, 1.30–1.49ct or 1.80–1.99ct. You'll get nearly the same visual size at significantly lower prices — and at Diamantwerp, our wholesale pricing already gives you up to 75% savings versus retail.
Carat vs. Size Perception
One of the most common misconceptions is that carat equals size. Carat measures weight, not dimensions. Two diamonds of identical carat weight can appear different sizes depending on their cut proportions and shape.
A well-cut diamond has optimal proportions that maximise its face-up appearance — the part you see when the diamond is set in a ring. A poorly cut diamond may carry more weight in its depth, making it appear smaller from above despite weighing the same. This is another reason why cut is the most important of the 4 C's.
How Diamond Shape Affects Apparent Size
Different diamond shapes distribute weight differently. Elongated shapes like oval and marquise have a larger surface area relative to their weight, making them appear larger face-up than a round diamond of the same carat weight.
The Points System
In the diamond industry, carats are subdivided into 100 "points". A diamond weighing 0.75 carats has 75 points. This system allows extremely precise measurements — critical for pricing, since even small weight differences can mean significant price variations.
When browsing our collection, you'll see weights expressed in both formats: a 0.53ct diamond might be described as "fifty-three points" or simply "half-carat range."
Total Carat Weight (TCW)
When shopping for jewellery with multiple diamonds, you'll encounter total carat weight (TCW) — the combined weight of all diamonds in a piece. A ring advertised as "2.00 TCW" might contain one 1.50ct centre stone with four 0.125ct accent stones.
Be cautious: a 2.00 TCW ring does not mean it has a 2-carat centre diamond. Always verify the weight of the individual centre stone, as this is what primarily determines the ring's visual impact and value.
Carat vs. Karat
A common source of confusion: carat (ct) measures the weight of diamonds and gemstones, while karat (K or kt) measures the purity of gold. 24-karat gold is pure gold, 18-karat gold contains 75% gold. Despite similar pronunciation, they refer to entirely different properties.
Our Recommendation
Consider diamonds just below the "magic numbers" — 0.90–0.99ct instead of exactly 1.00ct, for example. The visual difference is imperceptible, but the price difference can be significant. Invest those savings in a better cut grade for maximum sparkle.
At Diamantwerp, our wholesale pricing means you're already saving up to 75% compared to retail. This gives you the freedom to explore higher carat weights that would otherwise be out of reach — without compromising on cut, colour or clarity. Every diamond in our collection is certified by GIA, HRD Antwerp or IGI.
COMMON Questions
Frequently Asked Questions
What does carat mean in diamonds?
Carat (ct) is the standard unit of weight for diamonds and gemstones. One carat equals exactly 200 milligrams (0.2 grams). The term comes from carob seeds, which were historically used as balance weights due to their remarkably consistent mass. Carat measures weight only — not size or dimensions.
