Diamond Carat Weight: The Complete Guide

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If you wonder what is diamond carat, or what diamond’s size you should look for, you are in the right place. 

I personally gathered all the information you need about diamond carat, to help you better understand why it matters. We will cover some common questions and misconceptions, as well as doing price and size comparisons. If you don’t know how different carats look on the finger, I will give you one simple tool that will solve that issue. 

After reading this article, you can be sure you know what is the right carat for your budget. Let’s start.

Table of Contents

Diamond Carat Explained

One of the first questions we need to answer is “what is diamond carat?”. While a lot of people assume that a carat is the diamond’s size, it’s actually the diamond’s weight. In the diamond industry, we use carat measuring units to describe the diamond’s weight. In most cases, as the carat goes up, the price goes up, but it depends on other factors such as color, clarity and cut. When buying a diamond, it’s important for you to understand the carat measuring unit system.

  • 0.5 carat equals to 0.1 grams or 0.0035 ounces.
  • 1 carat equals to 0.2 grams or 0.007 ounces.
  • 2 carat equals to 0.4 grams or 0.013 ounces.

In the diamond world, it’s common to hear sellers and consumers talk in carat points. 

For example:

  • 0.58 carat equals to 58 points or to 0.116 grams
  • 1.35 carat equals to 135 points or to 0.27 grams
  • 2.12 carat equals to 212 points or to 0.424 grams

Diamond Size Chart: Carat Weight to MM

The following diamond carat-size chart can be used as a reference. By understanding the mm to carat comparison, it would be easier for you to know what to look for (based on your budget limits)

Please keep in mind that different diamonds share different diameters due to different cut levels and proportions. I created this mm to carat chart based on the average diameter of Ideal cut round diamonds.

Round Carat Weight Round MM Size
0.25 ct 4.0mm diameter
0.50 ct 5.1mm diameter
0.75 ct 5.8mm diameter
1.00 ct 6.4mm diameter
1.25 ct 6.9mm diameter
1.50 ct 7.3mm diameter
1.75 ct 7.7mm diameter
2.00 ct 8.1mm diameter
2.25 ct 8.5mm diameter
2.50 ct 8.9mm diameter
2.75 ct 9.0mm diameter
3.00 ct 9.3mm diameter
3.25 ct 9.5mm diameter
3.50 ct 9.75mm diameter
3.75 ct 9.9mm diameter
4.00 ct 10.1mm diameter

Diamond Carat Size Comparison On Finger

Need a diamond carat size comparison? JamesAllen has created a useful tool to help you see how an engagement ring with different diamond sizes would look like when worn on the finger and hand. If you want to use it, click here and enter to any diamond page you want. Choose the image of the hand below the main diamond image. It will open the carat size preview that allows you to control the size of the diamond on the ring. Note that the diamond has ideal cut measurements.

Does Diamond's Carat Weight All That Matters?

We all want to get the WOW factor when popping the question, and showing the diamond ring to friends and family. Yet, carat is not the only factor that determines whether a diamond is beautiful or not.

Let me explain.

A diamond with higher carat weight does NOT ALWAYS appear larger. For example, if you bought a 1.00 carat diamond of ideal cut and compare it with 1.00 carat diamond of a lower cut grade, you would see that the weight is being divided differently, which cause to different measurements and a different size of  “face-up”, as you see the diamond from the top.

Diamonds of lower cut grades may be too deep or too shallow, which results in poor brilliance. Since there is no point in getting a diamond with no brilliance and sparkles, I highly recommend you to play safe and look for a well-cut diamond, ideal cut or true hearts (also known as hearts and arrows) which have the most brilliance and fire.

How Carat Affects The Size Of The Diamond?

A diamond that is twice as heavy than another diamond, doesn’t mean it appears as twice larger. For example, you can see below, the size of a 0.50 carat diamond is approximately 5.1mm (if the cut is ideal), while the size of a 1.00 diamond is approximately 6.5mm. Although the carat weight is 2 times of the 0.50 carat diamond, it’s only 1.4mm larger or 27% larger. Still, the difference is very obvious when mounted in a ring. 

1 Carat Diamond's Price Chart: Color and Clarity Comparison

I created the following chart based on the most affordable option on the diamonds gallery from this website. After years in the business, I can tell they have the best prices in the market. Keep in mind, the most affordable diamond in the category isn’t necessarily a beautiful one, so take the prices as a reference only. The best way to know what you can get for your budget is to click here, enter your maximum budget, sort the diamonds by “carat: high to low”. If you need help, feel free to contact me here.

All diamonds are 1 carat, excellent/ideal cut, excellent polish, excellent symmetry with no fluorescence.

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Prices may change due to supply and market demand. Make sure to click here to see the current price

(Last updated: 26/02/2021)

Lab-Grown Diamonds vs Natural Diamonds: 1 Carat price comparison

We will do a side-by-side comparison of both natural and lab-grown diamonds. All diamonds are E color VS1 clarity with Ideal cut, Triple excellent with no fluorescence.

(last updated on 26/02/2021)

Diamond Type Natural Diamond Lab-created Diamonds % Price Gap
0.50 Carat E VS1 Ideal Cut $1,480 $640 56%
1.00 Carat E VS1 Ideal Cut $7,790 $2,460 68%
1.50 Carat E VS1 Ideal Cut $15,040 $5,670 62%
2.00 Carat E VS1 Ideal Cut $28,160 $10,840 61%

What Carat Should You Look For

If you ask yourself, “what carat should I get?”, the answer is simple. Based on your budget, you need to decide what you are looking to get:

  1. The largest diamond within your budget: Get a larger diamond with lower color and clarity
  2. Best balance between all factors: smaller diamond with good combination of color and clarity.
  3. Premium quality: A smaller diamond with the highest cut level (hearts and arrows), and better color and clarity

If you need help finding the right diamond, feel free to contact me here.

The alternative option is to get a much larger lab-grown diamond, with colorless color, beautiful cut and good eye-clean clarity for the same price.

Doing diamond research can be hard and frustrating, but can be very easy if you choose to buy your diamond online. Not only that it’s much affordable and you can save a lot of money, you also get the option to use advanced technologies, primarily the 360HD with the Super-Zoom which shows the exact color and clarity details of the diamond, so you can evaluate the diamond before you order it. JamesAllen offers a huge selection of diamonds (300,000+), both natural and lab-grown, and all diamonds are photographed with their leading, state of the art, 360HD and Super-Zoom, visualization technology.

“The bigger the better” is a rule that I like to follow. YET, you should never compromise on the cut of the diamond, the color and clarity (also known as the 4’c). Your goal is to find the best combination of the 4’cs within your budget.

Cut determines the brilliance of the diamond, which is an important factor in the WOW effect we all want to achieve when showing the engagement ring. Most women want to get at least 1 carat, but if you can’t afford to get it with the right combination of the 4’cs, you can choose a smaller diamond, for example a 0.90 carat, that has the right combination. If you insist on one carat, and you are short on budget, you can look for a “Very-Good” cut graded diamond, just make sure the diamond looks great on the Super-Zoom 360HD video.

Beautiful "Very-Good" Cut - 1.00 CARAT E-SI1 ($5,380)

Ugly "Very-Good" Cut - 1.02 CARAT F-SI1 ($5,410)

Other experts love to give specific measurements to look for. As I love to say, if it looks beautiful on the picture, it will look beautiful on the finger… and I’m telling you this as one who used to take hundreds of photos of diamonds on a daily basis. If the 360HD shows it is a beautiful diamond, then searching for specific measurements is a waste of time. Measurements were essential in the old world when diamond images were not available – they are not needed if you have the 360HD to enable you to choose the right diamond.  I recommend looking for an ideal cut diamond, colorless (D to F) or near-colorless (G to I) and eye-clean clarity, where inclusions are not visible to a naked eye.

In any case, JamesAllen has a 30-day return policy, so if you order it close enough to the proposal date, and you get it wrong, you can always send it back and replace it with the diamond she really wants.

How To Buy A 0.2 Carat to 1.5 Carat Diamond

What Is The Minimum Carat I Recommend

As long as you don’t have another diamond to compare your diamond to, you won’t be able to tell the exact carat weight of a diamond with a naked eye. For that reason, you can get slightly below the 1 carat mark, for example 0.97 carat, and save some cash that can be invested in the setting.

Can you guess what is the carat of the diamond on this video?

It’s a 0.25 carat diamond mounted on a yellow gold solitaire setting. If you ask me, it’s a gentle and classic option, and for an untrained eye, you could easily think it’s a 0.5 carat. As I showed you before, the average difference between 0.25 carat and 0.5 carat is 11mm. It’s a noticeable difference to the naked eye by all means, but only when comparing two diamonds.

The only question that matters is “Do you think it’s beautiful or not?”

How To Buy a Large Diamond

The Difference Between Carat Weight and Total Carat Weight

While carat weight refers only to the carat of the main stone, total carat weight (tcw) refers to the total weight of all the diamonds on the ring in carats. For example, if you have only 1 carat diamond, mounted on a solitaire ring, the total carat weight would be 1 carat. If you take the same 1 carat diamond, and mount it on a halo setting like this one, your total carat weight would be 1.52 carats. Same goes with diamond studs. If you ask for half a carat diamond studs, you’ll probably get a pair of 0.25 carat each.

Total carat weight vs carat weight


So that’s it. By now you should know that Carat is important, but most importantly is to get a diamond that shows good brilliance and sparkle. You can do that by getting a good combination of the 4 c’s: carat, color, clarity and cut. 

Remember I’m on your side if you need any help. Did I miss something? Let me know in the comments below and I will add it to this article ASAP.

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About the author: Yaniv Hadar

As a third-generation in the diamond industry, I’ve started my way in 2015 as a diamond photographer and seen hundreds of diamonds on a daily basis. Unlike other experts, I’ve had the opportunity to see any diamond you can think of: from the poorest to the rarest. Any size, any color. Using my knowledge and experience, I can show you how to pick the most valuable diamond for your budget while getting the most bang for your buck.

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