How Big is a 1-Carat Diamond?

When picking a diamond ring for any occasion, the carat weight is the most common term. And its use is quite every day in the gem trade, as the unit of measurement plays an integral part in the diamond retail business. So, it’s no surprise then that most people would mention carat first when purchasing a diamond, especially if they’re new to it. But depending on it alone also comes with one hiccup- it doesn’t always mean a similar result.

For instance, you could walk into a jewelry store and be shown a catalog or display of diamonds on such measurements. And you’ll find yourself gawking in confusion at the numerous size options available at the same carat. Then, you discover the universal truth about diamonds; they don’t all look the same size regardless of being equal carats. And because you want the best value, you may not be sure if picking the smaller or larger stones is the most logical approach.

Here, we’ll help you avoid such an embarrassing situation by showing you what to expect in terms of size when picking a 1-carat diamond. We’ll also explore the differences between a diamond’s carat and its physical size and talk about the determinants of how large each stone appears. Plus, we’ll answer whether size matters in a 1-carat diamond’s price and how to get the best for your buck when considering this factor in 1-carat diamonds.

Diamond Size vs. Diamond Carat

Before delving into answering how big a 1-carat diamond should be, let’s first differentiate between the two physical factors most people commonly misinterpret. The first fact to note is that a carat doesn’t necessarily determine the stone’s size, as it’s an entirely different quality. With this in mind, we can adequately define the two factors.

The carat (CT) is the unit of measuring a diamond’s weight, meaning it’s an indication of the stone’s approximate heaviness. One carat equals 200mg or 0.2g, and this standard number is presented as the stepping stone to valuing diamonds by weight. A 1-carat diamond will be any stone that reads approximately .20grams on a digital scale.

But you may wonder, what’s the difference between the weight and size? Are they so different? In a way, it’s a bit of yes and no. When two diamonds of extremely varying carats are placed side by side, the size difference is evident to the naked eye. But this isn’t always so in cases where the carat sizes are different by a slim margin. For instance, a 3-carat diamond will look more significant than a 1-carat diamond. But the difference may not seem evident to the naked eye when you have a 0.90-carat stone next to a 1.10 carat one. Accurate confirmation of the stones’ sizes comes into play. But then, what does this mean?

A diamond’s size has little to do with its heaviness and a lot to do with the total surface area. It’s a measurement of the stone’s length, width, and depth. In simpler terms, the size of a diamond has more to do with how it looks from the top and little with how heavy the stone is. Most people prefer to focus on the diameter size, but in the end, all aspects of a diamond’s size are measured in millimeters.

Understanding this difference helps you move to the next step of confirming a 1-carat diamond’s size. You’ll understand what leads to how a diamond appears large or small to the interested person.

Factors Influencing the Size of 1-Carat Diamonds

Because a diamond’s size dramatically affects how appealing it looks to an interested person, it helps to note the processes that bring about such an effect. The two main factors influencing a diamond’s size are its cut and shape. Both attributes are essential in selecting a 1-carat diamond and can mean the difference between an incredibly high-quality stone and a poor purchase. We’ll stretch further on these headings below;


The quality of diamonds is generally evaluated by measuring the 4Cs, which are cut, clarity, color, and carat. And of these four, the cut is most important in determining a diamond’s final size. Plus, it also contributes to other qualities, like how much light reflects and refracts through the stone or how radiant it appears in the presence of light. But let’s focus on its size-influencing capacity for this topic.

Depending on how impressive it is, a diamond’s cut is graded from Poor to Fair, Good, Very Good, Excellent, and Ideal. And most jewelers frown at stones graded Fair or Poor, as they don’t command good value. The aim is to produce a stone that hits the sweet spot between deep and shallow, and an Ideal or Excellent-cut 1-carat diamond will always command higher quality. But note that not all cuts of equal quality automatically mean they measure the same size. For instance, you could have five 1-carat diamonds, and their measurements can vary from 6.11 to as much as 5.53mm, even when the cut grade stands around Ideal, Excellent, and Very Good! To fully understand this, below is a table of five round 1-carat diamonds of equal color and clarity and how the cut can influence their sizes;

Cut GradeLength/Width RatioMeasurements (mm)
Good1.016.11 x 6.20 x 4.09
Very Good1.026.22 x 6.35 x 4.00
Excellent1.006.50 x 6.53 x 3.86
Excellent1.016.43 x 6.47 x 3.97
Excellent1.006.38 x 6.41 x 3.96

Notice the size difference of the stones, regardless of them being of the same weight and quality. Cut influences a diamond’s size when some stones are cut more profoundly, causing carat to be hidden at the bottom. A good-quality cut should yield a depth percentage below 62%, so the stone faces up the proper size. Ideal cut diamonds are always considered higher quality, even when they may not look as large as their lesser counterparts. 


Diamonds aren’t just cut to express an alluring design but are also shaped to suit different preferences. And each shape commands a unique measurement, thus pitting the sizes of 1-carat diamond stones against themselves. The numerous diamond shapes available include round, princess, emerald, cushion, Asscher, radiant, pear, marquise, oval, and heart. And when compared, the diameter would greatly differ, giving them distinct sizes when viewed from above. To display the differences, let’s look at the comparison table below for 1-carat diamonds of ideal cuts;

  • Round – 6.4mmPrincess – 5.5mm
  • Emerald – 6.5 x 5.0mm
  • Cushion – 6.5 x 5.0mm
  • Asscher – 5.5mm
  • Radiant – 6.5 x 5.0mm
  • Pear – 8.5 x 5.5mm
  • Marquise – 10.5 x 5.5mm
  • Oval – 8.5 x 5.5mm
  • Heart – 6.7mm

Of the many shapes, round diamonds are mostly considered the most valuable as they’re the traditional shape design. But when compared to options like emerald and cushion, they may look more petite. The difference is also is glaringly visible when paired with marquise diamonds. But they fair better compared to options like princess and Asscher.

Knowing these differences in cut and shape is the ultimate guide to purchasing the perfect size when looking for a 1-carat diamond.

Durand Shape Matter When Pricing 1-Carat Diamonds?

After confirming that you’re clear on how a 1-carat diamond’s size is measured, you may wonder if it affects the price. The answer isn’t as basic as you may feel. And though the general pricing unit is carat- that is, the diamond’s weight, it’s not always the only way to decide how much a stone should cost.

Yes, the weight does matter, but the cut and shape also play essential roles. For one, diamonds of higher cut grades will cost more than those of lower ones, regardless of their equal carats. And since they also influence how big or small a 1-carat diamond may look, you’ll want to go after the best grade for more value.

But when talking about the shape, it’s a different ball game. Round cuts are considered the most valuable diamond shapes, so 1-carat stones of these types will pull a high market value. But the other shapes are treated differently, and though they exhibit a fancier shape, they won’t draw more monetary value than round gems.

So, let’s answer the question above one by one. A higher grade equals a higher price and value in terms of cut. And in terms of shape, round cuts are pricier. But if you want more value for money, you would choose a larger-looking diamond for a lower price. Most fancy-shaped diamonds like marquise and oval would give you a wider diameter at a lesser price than a round one.

Of course, when considering shape and cut, it’s wise also to put the stone’s depth in mind. Round diamonds generally have the best depth, especially when ranked Excellent or Very Good. But they won’t always look as large as marquise, emerald, or oval stones, which display a wider diameter when observed from atop the crown. So, unless you’re satisfied with choosing quality over the size, you may want to have a rethink before making a final decision.

Getting the Best Size from a 1-Carat Diamond

The average size for a 1-carat diamond is 6.5mm, but note that this diameter refers to round stones. Fancy designs may offer smaller or larger sizes, depending on your option. And while the carat weight is a common way to measure value, it may not be the best choice when you’re looking to buy an engagement ring.

The goal in this aspect is to purchase a ring large enough to dazzle onlookers. And even when considering other qualities like clarity, color, and brilliance, you’ll still want a stone that stands out on the finger that wears it. It would help if you had some helpful tips on selecting the best size for 1-carat diamonds in all situations. And below, we’ll offer you the handiest suggestions.

Check the Measurements

Yes, it’s established that your budget only covers a 1-carat diamond, but don’t let it end there. Analyze each stone’s different size dimensions and pair this with other essential factors. Combine the categories you desire for starters, including the carat weight, cut grade, and ideal parameters. Then cross-compare the stones available and choose an option that ranks above average.

You can also use the old-fashioned technique by measuring the diamond’s size with a ruler. Since this aspect deals with the diameter and surface length, it’ll be easier for you to confirm.

Don’t Sleep on Quality

It’s one thing to want a 1-carat diamond large enough to wow your admirers. But it’s another thing to purchase a stone of low quality. Don’t be carried away by the length or width of the stone, but also consider if its cut, clarity, brilliance, fluorescence, and color also match the price.

You’ll want an Ideal or Excellent-cut diamond when dealing with the size, as this grade offers the best refraction and reflection, plus gives the most impressive evenness. And for ideal parameters, check for a depth below 62% if you’re dealing with round diamonds. It’s no use having a large diamond if its refractive abilities are poor because the cut is too shallow. So, gun for a great cut to gain extra brilliance and sparkle in your chosen diamond.

Go for ‘Spread’!

Marquise, oval, and pear-shaped diamonds measure the largest sizes, and they’ll give you the best size value for a 1-carat diamond. This attribute is often called ‘spread’ and describes how big a diamond appears. But when picking them, the second suggestion above still applies. Try avoiding a stone that’s too ‘spread’ by always considering the best cut grade and ideal parameters when choosing. This way, you can bank on the best depth for your stone, thus ensuring you get more brilliance, radiance, and sparkle for less price.

The sweet spot for depth and avoiding excess spread in a diamond differs from its proposed shape. To clarify, here’s a quick overview of what to go for and what to avoid regarding the depth in different diamond shapes;

ShapeToo ShallowToo DeepPerfect
RoundBelow 61Above 6259 to 62
AsscherBelow 61Above 6761 to 67
OvalBelow 58Above 6258 to 62
EmeraldBelow 61Above 6761 to 67
MarquiseBelow 58Above 6258 to 62
PearBelow 58Above 6258 to 62
CushionBelow 58Above 6258 to 62

By this parameter, shapes displaying the lowest numbers offer the best spread. But this factor is kept at a controlled depth of 62%, as anything more than that may constitute a shallow cut in some stones.


It’s normal to wonder how big a 1-carat diamond would be, especially considering the numerous shapes and cut they come. But understanding how to compare the diameter and depth of each type is the key to getting the right gem for your need. Of course, round diamonds are the standard parameters for measuring a gem’s size, but it doesn’t mean they’re your only choice. Here, you can pick helpful tips that’ll guide you into deciding what shape is the best size value when choosing a 1-carat diamond.