0.90 vs 1 Carat Diamonds: How to Decide

The main difference between a 0.90 and 1 carat diamond is a 1 carat diamond has a slightly longer diameter, often 0.2 mm wider than a 0.90 carat diamond. They generally appear identical to the naked eye because the distinction in weight and size is so minimal.

My recommendation is to choose a 0.90 carat diamond instead of 1 carat because they offer better value. When I was shopping for my wife’s engagement ring, I intentionally aimed for a diamond that fell short of the 1 carat mark because I could avoid the premium price.

So let’s compare 0.90 versus 1 carat diamonds across their most important characteristics, including dimensions, price, popularity for engagement rings, and more.

Size, Dimensions, and Proportions

The size of a diamond is generally referring to its weight, because that’s the primary way it’s measured. 

If you’re speaking with a jeweler about a group of diamonds, they won’t first describe them by the width of its table or the height from the culet to the crown.

As you can see from the image below, it’s a confusing way to describe its size and doesn’t convey much to the average buyer.

Instead, the jeweler will identify them by carat weight. One carat equals 0.2 grams, so a 0.90 carat diamond weighs 0.18 grams.

This slight difference in weight does affect its overall dimensions.

To demonstrate, we’ll compare the measurements of two diamonds.

This 0.90 carat diamond, from the jeweler where I bought my wife’s round-cut diamond engagement ring, is viewable in high-resolution from every angle.

Its measurements are 6.13 – 6.21 mm x 3.80 mm.

The first number is its minimum diameter, and the second is the maximum. 

The third measurement, 3.80 mm, is its depth. A diamond’s depth is the height from the table to the culet.

Now we’ll compare it to this 1 carat diamond.

Its dimensions are 6.32 – 6.37 mm x 4.00 mm.

The extra 0.10 carats do result in a wider diamond with more depth, but the differences aren’t noticeable in most cases.

For instance, if a jeweler showed you a single diamond and you were told it was either 0.90 or 1 carats, it’d be difficult to give the correct answer.

Price

Carat weight is one of the most impactful qualities on a diamond’s price. It doesn’t increase linearly. 

Instead, it’s exponential, where a one carat costs more than twice as much as a 0.50 carat diamond, and the price more than doubles from 1 to 2 carats.

To provide examples, I compiled prices for more than 500 diamonds with the same traits, except they had different carat weights. Their average prices are in the chart below.

To provide a price comparison for 1 carat versus 0.9 carat diamonds, I analyzed prices for 337 diamonds from my number one recommended jeweler, James Allen.

They had the following qualities:

• Cut: Ideal
• Clarity: VS1
• Color: G
• Fluorescence: None
• Grading lab: GIA

The average price for the 1 carat diamonds was $8,834, with a range of $7,740 to $12,470.

For 0.90 carats, the average was $5,977. The lowest price at that carat weight was $5,170, and the highest was $7,400.

On average, that’s a 48 percent premium for a 1 carat diamond over one that weighs 0.90 carats. Even though the 1 carat gem weighs only 11 percent more, it costs almost double the price.

The reason there’s such a significant price difference is because jewelers know there’s more demand for 1 carat. 

There’s a sense of prestige a full carat carries. Many buyers pay a higher price for that satisfaction.

Popularity in Engagement Rings

The average carat weight for an engagement ring diamond is close to 1 carat.

Estimates differ, but you’ll generally see it placed between 1 and 1.09 carats.

Take this 1 carat engagement ring as an example.

When placed in the 14K white gold solitaire setting, the diamond commands all the attention. 

At this size, you don’t have to worry about it appearing small or feeling compelled to add more diamonds to the piece.

For engagement ring diamonds less than one carat, it’s common to include features like a halo or pave diamonds.

The additional gems add weight to the piece without the same price increase that would result from choosing a 1 carat diamond.

But it’s important to emphasize this isn’t essential for a stunning engagement ring. In general, you’d need to add about 20 percent to a diamond’s carat weight before it’s noticeable.

For example, when I bought my wife’s engagement ring, I have to admit: It appeared smaller than what I was expecting. When I connected with the store representative, he was helpful in explaining this principle to me.

Although I was considering moving up the carat weight, he was willing to turn down an upsell opportunity to convey this idea. I stuck with my original purchase, and I’m glad I did.

Color Grade

A diamond’s color grade indicates the presence of yellow or brown in its facets. 

The Gemological Institute of America (GIA) developed a scale from D to Z, where D means colorless and Z identifies strong color.

Each grade is placed in one of five categories:

• Colorless (D-F)
• Near colorless (G-J)
• Faint (K-M)
• Very light (N-R)
• Light (S-Z)

As a buyer, don’t concern yourself too much with a specific color grade. Instead, it’s about finding a 0.90 or 1 carat diamond that appears colorless without magnification.

In both cases, diamonds graded H or above often meet this standard.

For example, view this high-quality image of a 1 carat diamond with an H color grade.

Now compare it to this one that earned a D.

It’s difficult to distinguish their color.

The same is true for 0.90 carat diamonds because in general, higher carat weights require improved grades to appear eye-clean.

The reason I recommend near colorless diamonds, as opposed to colorless, is because of value. 

You’ll avoid the price increase for a colorless diamond, but it’ll look identical.

Clarity

Diamonds earn clarity grades that identify the extent to which inclusions, also called clarity characteristics, affect its appearance, brilliance, and durability.

The GIA scale ranges from flawless to I3, where each step down the scale indicates more impactful blemishes.

In most cases, I recommend starting your search with SI1 clarity diamonds for both 0.90 and 1 carats because there are ones where inclusions aren’t visible to the naked eye. 

You might have to work your way up the scale (I landed on a VS1 clarity for my wife’s diamond), but you can find tremendous value with SI1 or VS2.

It may have several pinpoints scattered across the table or a transparent feather on the pavilion.

But if small enough, they’re only visible at 10x magnification.

To provide a real example, here’s a 1 carat diamond that earned a VS2 clarity grade.

The clarity plot on its report shows crystals, feathers, needles, indented naturals, and naturals.

But each instance is small. They’re likely invisible when viewed in a normal setting.

If you place it next to a 0.90 carat diamond that earned a VVS1 clarity grade, you can’t distinguish between them. 

But you’d pay up to 50 percent more for that improved clarity grade.

How to Decide

Deciding on a 0.90 versus 1 carat diamond involves understanding how the slight difference in weight affects its price, appearance, and performance.

Here are some guidelines to help.

Opt for a 0.90 carat diamond if:

• You aren’t concerned about reaching the 1 carat threshold and want to save between 30 and 50 percent on its price
• You’re interested in increasing the total carat weight of the piece with diamond accents in the form of a halo or pavé
• You understand it’ll appear almost identical to a 1 carat diamond

Explore 1 carat diamonds if:

• You want the satisfaction of a full carat
• You’re willing to pay the premium compared to a diamond with a slightly lower carat weight
• You’re interested in a diamond that often stands alone in a solitaire setting and choose not to complement it with other gems

Following these tips will help you find the perfect diamond for your occasion.

“Choosing the right carat weight is like finding the perfect note in a symphony—it should resonate with your personal style and the occasion it celebrates. A 0.90 carat diamond often sings the same sweet tune as a 1 carat stone but at a more harmonious price point.”

— Chuck Harris, Teach Jewelry Team Member

Q&A .9 Carat vs 1.0 Carat

Q1: Why do diamond prices increase exponentially with carat weight, and how does this affect the market for diamonds just below full carat weights?

A1: Diamond prices increase exponentially with carat weight due to the rarity of larger diamonds. As diamonds increase in size, they become harder to find, and their price reflects this scarcity. This creates a niche market for diamonds just below full carat weights, like the 0.90 carat stones, which can be significantly less expensive than their 1 carat counterparts while offering almost the same visual impact.

Q2: How does the cut of a diamond influence the perception of its size and brilliance, especially when comparing diamonds close in carat weight like 0.90 and 1 carat?

A2: The cut of a diamond greatly influences its brilliance and how large it appears. A well-cut diamond can appear larger and more brilliant because it’s proportioned in a way that maximizes light return. Therefore, a well-cut 0.90 carat diamond might seem just as large or even larger and brighter than a poorly cut 1 carat diamond.

Q3: In what scenarios might a consumer prefer a 0.90 carat diamond over a 1 carat diamond aside from price considerations?

A3: A consumer might prefer a 0.90 carat diamond over a 1 carat diamond if they are looking for a more subtle size or if they want to allocate more of their budget towards a higher quality cut, clarity, or color grade. Environmental or ethical considerations might also play a role, as some consumers may opt for a slightly smaller diamond if it’s sourced in a more sustainable or ethical way.

Q4: Are there specific diamond shapes that make a 0.90 carat diamond appear larger, and are these shapes also ideal for 1 carat diamonds?

A4: Certain diamond shapes, like the oval, marquise, or pear, can appear larger than round diamonds of the same carat weight due to their elongated cuts. These shapes can maximize the surface area visible from the top, making the diamond appear larger. These shapes are ideal for both 0.90 and 1 carat diamonds, especially if the goal is to maximize perceived size.

Q5: Can the type of precious metal chosen for the setting influence the perceived size or color of a 0.90 carat diamond compared to a 1 carat diamond?

A5: Yes, the precious metal can influence the perception of the diamond’s size and color. For example, a white gold or platinum setting can enhance the diamond’s brilliance and make it appear larger and whiter, while yellow gold can complement warmer colored diamonds. The choice of metal should complement the specific characteristics of the diamond to enhance its overall appearance.