Diamond Carat: Learn the Facts to Buy Sensibly

Understanding diamond carat...

We’ve all heard the phrase, “Bigger is better”. It usually applies to every luxury item in life: larger homes, pricier cars, high fashion, etc. As such, many strive to find diamonds with the largest carat they can afford, so others marvel at the massive, glistening gem. There’s only one problem: a diamond’s carat does not dictate its size!

Ring in a Jewelry Box: Diamond Carat Education

💡Contrary to popular belief, the carat and size of a diamond are mostly unrelated, but similar factors affect the measurement of each. However, these characteristics can drastically impact a diamond’s price and value.

In this article, we’ll discuss:

  • What is a diamond carat and where does it come from?
  • Average proportions of round diamonds at different carat weights.
  • How does carat affect a diamond’s price?
  • Diamond carat buying tips.

The basics: What is diamond carat?

Carat, also known as carat weight, measures a diamond’s overall weight. A “carat” is 200 milligrams, and each carat consists of 100 “points”. These points are all of the potential decimal weights you may encounter while diamond shopping: 1.23, 4.79, .82, etc. Finally, the GIA and gemologists often shorten carat weight to “ct.” on grading reports.

Origins of the carat

Carat may seem like an odd unit of measurement for the weight of a diamond, but it’s actually based on a historic unit used in trading for centuries!

In fact, the word “carat” derives from carob, a type of locust tree that produces seeds. Because the seeds were a standard weight, traders used them to measure goods on routes and in markets. One “carat” was the weight of one carob seed.

However, as the use of the carat spread to other parts of the world, the measurement became less accurate. People used carob seeds from different types of locust tree, which meant the measurements were no longer uniform and a “carat” was more of a weight range than an actual number.  

👉🏻As such, the carat required standardization, and so the carat became the uniform 200 milligrams internationally in the 20th century.

Diamond carat size chart: Carat weight vs. diamond size

Is there a relationship between carat weight and diamond size?  

Yes, but it’s complicated. Because carat weight is not the same as diamond size, two gems with equal carat weights may have different lengths, widths, etc.

Jeweler Using Tool to Checking the Diameter Size of a Diamond
Jeweler checking the size of a diamond.

The importance of cut when discussing carat weight and size

So why can two gemstones have the same diamond carat weight and different sizes? ✅The answer: their cut! The technique used in the diamond cutting process can vary by gem cutter, and craftsmen value and emphasize opposing diamond characteristics.

In truth, you can have three 1 carat, round brilliant diamonds that look different in both size and sparkle. A diamond’s cut can be too shallow or too deep, or there may be issues like a thick girdle. To preserve carat weight, some gem cutters craft their diamonds disproportionately. However, in doing so, they can impact the diamond’s fire, scintillation, and brilliance.  

However, there are typical size ranges for rounded diamond carats that you can use to understand whether a stone might have a poor cut. To avoid buying a disproportionate diamond, GIA grading reports and assistance from your jeweler can be helpful in understanding the typical measurements of a diamond in your chosen carat weight. It’s important to examine a diamond’s cut yourself to ensure you are purchasing a quality stone!

Fancy shapes and carat weight

While the round brilliant diamond has been the most popular option among buyers for decades, many people are now buying fancy shaped diamonds to set themselves apart. These shapes, such as the pear, marquise, oval, heart, etc., impact how large a stone appears regardless of diamond carat weight.

Some fancy shapes, such as the oval, pear, and marquise, have elongated tables that add length to a diamond. As such, these gems appear larger than expected at their respective carat weight. Another good example of this effect is the emerald cut diamond, which has a broad, long table that looks much larger than other cut stones of the same weight. Additionally, these fancy shaped stones make slender fingers look even longer!

As previously mentioned, each diamond shape has its own range of average sizes. Lengths, widths, and percentages may vary slightly, but overall there is an ideal range for each shape.

How big is a 1 carat diamond?  

Here is a chart detailing the average sizes of the round brilliant diamond for your reference:

Before having a more accurate perception of the sizes:
Place a credit card or coin on the screen according to the template below. Use the + and - buttons to adjust the scale until your card or coin matches the corresponding template on the screen.
Standard Credit Card (85.60×53.98mm)
Standard credit card (85.60×53.98mm)
U.S. Lincoln Penny/Cent Obverse 2019 (19.05 mm)
U.S. Lincoln cent (Diameter: 19.05 mm)
5 Euro Cent Coin (21.25mm Diameter)
5 euro cent coin (Diameter: 21.25mm)
0.25ct - 4.0mm (Diamond Carat Size)
0.25 ct
0.5ct - 5.1mm (Diamond Carat Size)
0.5 ct
0.75ct - 5.8mm (Diamond Carat Size)
0.75 ct
1.0ct - 6.4mm (Diamond Carat Size)
1.0 ct
1.25ct - 6.9mm (Diamond Carat Size)
1.25 ct
1.5ct - 7.3mm (Diamond Carat Size)
1.5 ct
1.75ct - 7.7mm (Diamond Carat Size)
1.75 ct
2.0ct - 8.1mm (Diamond Carat Size)
2.0 ct
2.25ct - 8.5mm (Diamond Carat Size)
2.25 ct
2.5ct - 8.9mm (Diamond Carat Size)
2.5 ct
2.75ct - 9.1mm (Diamond Carat Size)
2.75 ct
3.0ct - 9.3mm (Diamond Carat Size)
3.0 ct
3.25ct - 9.5mm (Diamond Carat Size)
3.25 ct
3.5ct - 9.75mm (Diamond Carat Size)
3.5 ct
3.75ct - 9.9mm (Diamond Carat Size)
3.75 ct
4.0ct - 10.1mm (Diamond Carat Size)
4.0 ct

How does diamond carat affect the price?

Diamond carat does have a direct effect on a gem’s price. However, quality plays a large role in value as well, and the two factors greatly change the price of comparable diamonds.

The effects of carat weight on diamond price

First, as carat weight increases, so does price. So how much is a 1 carat diamond? Diamond price per carat typically starts around $2,000 - $2,500, but it rises quickly. In fact, diamond prices tend to rise exponentially rather than in a linear fashion, as larger gems are hard to come by. 📈 

Large, heavy diamonds of decent quality are rare, and even the price difference between .5 carat and 1.0 carat diamonds can be astronomical. If you’re looking at 1 carat diamonds and wondering if you should look at larger stones, remember that a diamond twice the weight of your current choice will likely cost about four times as much!

While this rule is consistent across all diamond shapes, fancy shaped stones cost less than round brilliant gems. Since their longer tables also tend to make diamonds appear larger, fancy shapes are a great value for those who can’t afford heavier diamonds.

The other 3Cs and diamonds of equal carat weight

Although carat weight is the largest factor in diamond price, cut, color, and clarity also play a role in the value of diamonds.

When comparing three different diamonds that all weigh 1 carat, you may find that they vary wildly in price.  These diamonds are probably very different in quality, and how refined a diamond’s other features are will determine how brightly your gem will sparkle.🌟

1 Carat Diamond With Lesser Qualities (Blue Nile LD13030556)
1 Carat Diamond With Good Quality Gradings (Cut, Color and Clarity) - Blue Nile LD14390380

1 carat diamonds sold at $2,391 (L) and $7,173 (R) | Images: Blue Nile

For instance, take a look at this diamond and this diamond. They are the exact same carat weight, but the second diamond is $5,000 more expensive than the first! That is because the cut, color, and clarity of the second diamond are top-notch, while the first stone has some lesser qualities. Understanding how the other 3Cs affect the diamond search is crucial to buying sensibly.

Priced right: “Magic sizes” vs. “Under sizes”

Buyers feel drawn to diamonds with “magic” or perfect sizes. Rounded, quarter, or half carats sell extremely well, and the allure of the 1 carat diamond traps first-time buyers constantly. Due to demand for these sizes, they tend to price higher than other diamonds, meaning there’s a chance that you can save money by purchasing just under your desired size.

However, it’s important you play this pricing game carefully. Typically, you can save money by buying a diamond just under a whole or half carat, saving as much as 25%. But, as people begin to notice this trend and purchase these “under size” diamonds, the prices are creeping upward!

Diamond carat buying tips

Although advertisements emphasize the supposed importance of diamond carat, it still is the most objective characteristic of the 4Cs. Many correlate it with a diamond’s perceived size, and they’re drawn to larger gems that seemingly represent their status, wealth, or endless love.

But is it really the most important factor in diamond buying?

Diamond carat and diamond cut: What should you prioritize?

So if diamond carat is so important to many buyers, should it be prioritized over diamond cut? Diamond cut is the most crucial characteristic for your gem to sparkle brilliantly. If you’re most concerned about how large your diamond appears, then opt for a higher carat weight and lower cut quality. But, you may regret it once you see your diamond shine compared to smaller stones with better cuts!

Cut dictates how light travels through your diamond, and it’s the catalyst for fire, brilliance, and scintillation. If you want a quality diamond, it’s best to prioritize cut over other factors.⚖️ Then, find a healthy mix of color and clarity, followed by carat.

Diamond Carat vs. Cut: A Brilliant Diamond Ring Surprising a Female
An Excellent cut can even mask lesser quality color and clarity, so it really is a saving grace!

Saving money on diamond carat

If you want a larger diamond, you’ll just have to pay more. It’s a fact of the jewelry industry, and sacrificing color and clarity for a quality cut, heavier stone is a common occurrence.

However, if you still want to stick to a budget, here are a few ways to save on diamond carat:👇🏻

Stick with brilliant cuts and specific settings

Be sure to buy cuts that highlight your diamond’s brilliance. Brilliant cut diamonds will sparkle the most, so if you’re worried about your diamond appearing dull, they’re a great option to conceal issues.

Additionally, the setting of a diamond changes how large it appears. Choose a halo setting to make smaller diamonds appear larger. Diamonds encircled in accent stones have a very lavish feel, so you’ll feel as though you spent more overall!

Another great setting for smaller diamonds is the solitaire setting. Find one that elevates the diamond within the setting, with pinched metal or a thin band. Thinner metal around your diamond will make it appear larger.

“Under size” your diamond

Opt for a diamond just below the ”magic numbers”. A diamond that measures .9 carats can look identical to a 1 carat stone, so it’s an easy way to save budget without sacrificing your gem’s appeal.

However, as more buyers start using this process, the demand for diamonds right outside the “magic size” increases, and it might be difficult to get a good deal. Be mindful of prices per carat!

Choose fancy shapes

Delicate, long fancy shapes make buying a smaller diamond a breeze!

Ignore the pricey round brilliant diamond and opt for a marquise, emerald, or even heart shaped diamond. Doing so will save you some money, but you’ll have a diamond that appears larger than its carat weight due to its unique silhouette.

Total carat weight vs. carat weight

Be careful of pieces that list the diamond’s “total carat weight” rather than its carat weight! Total carat weight (ctw, tcw, or CTTW) is the weight of all diamonds in a setting. If you have more than one diamond on a setting, such as side or accent stones, it means they are included in this number.

In contrast, carat weight is the weight of just one stone. 🧐If you have more than one diamond on your setting, make sure you know both the carat weight of your main stone and the carat total weight of the entire piece. Both numbers are important for understanding how much value you’re getting.

Keep the wearer in mind

Whatever diamond you buy should fit the wearer, and those individuals with smaller hands can actually wear diamonds of a smaller size. Because of their smaller hands, diamonds with lower carat weights actually look bigger on their fingers!

Preview the Carat Size on Wearer's Finger
James Allen

As previously mentioned, fancy shapes with longer silhouettes will appear longer on slender fingers, so make sure you do not spend more than you need to for a large diamond.

Counting carats isn’t always wise

So is bigger really better when it comes to diamonds?

When diamond shopping, it’s important to remember that quality trumps size. While diamond carat weight and size are not the same, people equate the two and shop for the highest carat diamond within their budget. However, by ignoring cut, color, and clarity, they can end up purchasing a diamond of lower quality that won’t sparkle as intended!😲

Diamond carat is a feature to consider while shopping, but a .5 carat diamond can make you just as happy as a 5 carat stone if it carries the fire, brilliance, and scintillation that people desire.

If you still wish to buy a high carat stone, just make sure you inspect it yourself and find a gem with a GIA grading report so you can know the specifics. Take a look at our articles on cut, clarity, and color for more information on how to purchase a diamond smartly.

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