Diamond Carat Guide
Discover the details of carats: the unit of measurement used to describe diamond weight.
IN THIS GUIDE
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Diamond Carat vs. Diamond Size
Carat Definition: What Is a Carat?
While many confuse carat as a measurement of physical size, it is actually a measurement of weight used to describe diamonds and other gemstones. One carat equals 0.2 grams, about the same weight as a paperclip.
To understand what diamond carat measures, it’s helpful to know the origins of the carat system. It began with carob seeds that early gem traders used as small, uniform counterweights to their balance scales. At that time, gemstone measurement varied internationally; there was no standard. It wasn’t until 1913 that the world adopted the modern metric carat. Now, a carat weighs the same in every corner of the globe.
As one of the four factors that describe and determine a diamond’s quality and value, carat should not be confused with ‘karat,’ a unit used to measure the purity of gold.
Diamond Carat vs. Diamond Size
Millimeters vs. Carat Weight Measurements
Understanding the difference between millimeters and carat weight is important for anyone shopping for jewelry. Millimeter (mm) measurements reflect the gemstone's dimensions, while carats measure weight.
While carat weight influences a diamond’s appearance, it doesn’t directly equate to size. Two diamonds of the same carat weight can look different based on how their weight is distributed. For instance, elongated fancy-shaped diamonds with shallow depths and longer dimensions may appear larger than round diamonds of the same carat weight.
Because other gemstones have unique densities, they can appear larger or smaller than diamonds of the same carat weight. Denser gemstones, like rubies and sapphires, weigh more than diamonds of the same millimeter dimension—for example, a 5 mm ruby will weigh more than a 5 mm diamond.
How Is Diamond Carat Measured?
One carat is 200 milligrams, and each carat is divided into 100 ‘points’ to allow exact measurements to the thousandth decimal place. To ensure precision, accuracy, and consistency, diamond carat is measured by professionals with specialized micro-balance scales.
The slider above allows you to see how the diamond appears as its carat weight is adjusted. By moving the slider, you can zoom in or out to simulate the appearance of a diamond at different carat weights, reflecting how its size would change.
Understanding Diamond Carat
While many confuse carat as a measurement of physical size, it is actually a measurement of weight used to describe diamonds and other gemstones. One carat equals 0.2 grams, about the same weight as a paperclip.
To understand what diamond carat measures, it’s helpful to know the origins of the carat system. It began with carob seeds that early gem traders used as small, uniform counterweights to their balance scales. At that time, gemstone measurement varied internationally; there was no standard.
It wasn’t until 1913 that the world adopted the modern metric carat. Now, a carat weighs the same in every corner of the globe.
As one of the four factors that describe and determine a diamond’s quality and value, carat should not be confused with ‘karat,’ a unit used to measure the purity of gold.
What Does CTTW Mean?
CTTW, TCW, and TW are all abbreviations for ‘Carat Total Weight.’ CTTW references the combined weight of all diamonds within a piece (or pair) of jewelry where more than one diamond is used.Diamond stud earrings, for example, are typically quoted in CTTW, which indicates the combined weight of both earrings within the pair.
Diamond Size Chart
Diamond Size Chart
This chart estimates the average size of differing diamond shapes in various carat weights. Each image shows what it looks like when viewing the diamond from the top down. As you’ll notice, two diamonds may appear to be different sizes with the same carat weight — this is because shape (in addition to density and depth) plays a big role in how carat weight is visually represented.
Actual Carat Size on Hand
How Important Is Diamond Carat?
Diamond carat can be very important for customers. As one of the 4 C’s (cut, color, clarity, and carat) used to describe and determine a diamond’s quality and value, carat weight often has a significant impact on price.
For example, if the cut, color, and clarity remain the same, a diamond’s price will doubtlessly increase with carat weight — as larger diamonds are much rarer. That said, if the cut, color, and clarity vary, two diamonds with the same carat weight can have very different prices.
How Diamond Carat Impacts Price
As mentioned, carat weight has a significant impact on price. Larger diamonds are much more valuable because they are discovered in nature less frequently than small diamonds. This means that diamonds are not priced linearly — a one-carat diamond will cost more than two half-carat diamonds of the same quality.
Carat’s impact on price is clearly displayed when considering what the diamond industry refers to as ‘magic sizes.’ At certain weight boundaries (a ½ carat, ¾ carat, and 1 carat), or ‘magic sizes,’ the price per carat increases dramatically. These set boundaries coincide with popular weights, which means greater demand and even greater prices. For example, if one diamond weighs 0.97 carats and another of the same cut, color, and clarity weighs 1.03 carats, you probably wouldn’t be able to tell the difference between the two. However, the cost difference will be significant because the second diamond is over the ‘magic’ threshold of one carat
Is Carat the Only Factor That Affects the Size Appearance of a Diamond?
No, carat weight is not the only factor that affects the size appearance of a diamond. A diamond’s shape, depth, and symmetry also affect how big (or small) a diamond looks.
Elongated shapes (such as oval and emerald) appear larger than 1:1 diamonds (such as round) because elongated shapes can carry most of their weight in their length as well as their depth.
Two diamonds of the same shape with different depths will also have different size appearances. For example, a one-carat pear with a shallow depth will look much larger than a one-carat pear with a deep depth.
Both depth and shape are factors listed on a diamond’s official certification report. Reference them to maximize size without the added cost of extra carat weight.
How to Make a Diamond Look Bigger
More Tips on How to Make a Diamond Look Bigger
Halo Settings: Choose a halo setting that features smaller diamonds that surround the center stone in shimmering light to increase the size appearance of your center stone.
Delicate Bands: The smaller the band of your setting, the larger your stone will appear. If the band of your setting is thick, it will draw attention away from your center stone and make it seem relatively small compared to the band.
Consider a Lab Created Diamond: With lab diamonds, you can purchase a much higher carat weight for a lower price than a smaller natural diamond. Optically, chemically, and physically the same as their natural counterparts, lab diamonds are an excellent option for anyone looking to make a big statement with their center piece at a more accessible cost. Learn more in our Lab Grown Diamond Guide.
Consider a Diamond Alternative: A popular, visually similar alternative to diamonds is moissanite. While moissanite is compositionally quite different, it does feature a fiery, beautiful appearance that many mistake for the brilliant appearance of diamonds. Learn more in our Moissanite vs. Diamond Guide.
Regular Cleaning: Ensure that your diamond sparkles brightly by following tips on proper cleaning and care. A dull, dirty ring may look less impressive and smaller than a shimmering, clean ring.
Diamond Carat FAQ
FAQ
What's the average carat size for engagement rings?
The average carat for engagement rings is around 1.5 carats. The average lab diamond engagement ring is typically slightly larger than its natural counterparts.
How much is a 1-carat diamond ring?
The average cost of a1-carat natural diamondring is $7,500. The average cost of a1-carat lab diamondring is $3,500.
How much is a 1.5-carat diamond ring?
The average cost of a 1.5-carat natural diamond ring is $13,000. The average cost of a 1.5-carat lab diamond ring is $5,500.
How much is a 2-carat diamond ring?
The average cost of a 2-carat natural diamond ring is $20,500. The average cost of a 2-carat lab diamond ring is $7,500.
How much is a 3-carat diamond ring?
The average cost of a 3-carat natural diamond ring is $36,500. The average cost of a 3-carat lab diamond ring is $13,000.
How much is a 4-carat diamond ring?
The average cost of a 4-carat natural diamond ring is $48,000. The average cost of a 4-carat lab diamond ring is $19,000.
Carat vs. karat: what is the difference?
Carat and karat sound alike; however, they measure completely different things. One measures weight and one measures gold purity. Let’s break down what each term means and why they matter when you’re buying jewelry:
- Carat: A carat (ct) is the standard unit for measuring gemstone weight, with one carat equal to 200 milligrams (0.2 grams). In modern jewelry, carats provide an exact measurement of a stone’s mass, though this doesn’t directly translate to its visible size or dimensions. For instance, a 1-carat round diamond may appear different in size from a 1-carat oval diamond, even though they weigh exactly the same.
- Karat: Karat (K) measures the purity of gold in an alloy, expressed as parts per 24. Pure gold is designated as 24K, meaning all 24 parts are gold with no other metals present. For example, 18K gold contains 18 parts pure gold and 6 parts other metals, making it 75% pure gold. This system allows jewelers and consumers to understand the exact composition of gold jewelry and helps determine its value and durability.
The primary distinction between these terms lies in their measurement purposes. Carats measure physical weight using precise decimals (such as 1.75 ct), while karats measure gold purity typically in whole numbers (10K, 14K, 18K, 24K).