If you are having problems with visualizing actual diamond sizes in real life, you’ve come to the right place. We have compiled diamond weight charts for the most popular diamond shapes in the market!
Note: depending on your screen resolution, the actual size seen may vary.
Currently, the standard 57 facets round brilliant cut is the most popular choice of shape. Due its cutting style that’s optimized for brilliance and dispersion, round brilliants make up for more than 60% of all diamonds sold in the world.
Now, I want to address a common misconception that people have when shopping for diamonds. Just because a diamond is twice as heavy as another stone, it doesn’t mean it will look twice as large as the other.
As you can see above, the size of a 1 carat diamond is approximately 6.5mm (based on the assumption that the stone is cut to ideal proportions). On the other hand, the size of a .5 carat diamond is approximately 5.2mm. Even though the carat weight is 50% of a 1 carat stone, it doesn’t face up twice as small!
Likewise, the physical size of a 2 carat diamond (8.2mm diameter) isn’t twice as big as that of a 1 carat diamond (6.5mm diameter). Hopefully, this clears up the misunderstanding of carat weight and actual sizes.
James Allen has created a useful graphic illustration to help you see how an engagement ring with varying diamond sizes would look like when worn. Click here to find out more…
For people who are looking up carat size to mm information for fancy cut diamonds, we had also compiled some useful reference data on this page. What I want to highlight here is that the dimensions/diameters shown here are based on “ideal” length to width proportions.
You need to understand that the “best” length to width ratios for fancy shaped diamonds are largely up to personal tastes and there’s no right or wrong if you prefer a particular look.
Let me illustrate by using the heart shaped diamond as an example…
In our charts, the dimensions of a 1 carat heart shaped diamond is indicated as 6.50mm x 6.50mm. This is based on a length to width ratio of 1:1. Most people (including myself) prefer fatter looking stones with length to width ratios of around 0.90:1.
Obviously, the dimensions of a 0.90 l/w ratio heart diamond would no longer be 6.50mm x 6.50mm. In this case, a heart shaped diamond may exhibit dimensions of 6.15mm x 6.80mm and this is perfectly acceptable.
I want you to get this straight before you commit an expensive mistake when buying diamonds. The carat size to mm chart should only be used for visualization purposes and not as a tool to help you select a diamond.
90% of diamond consumers prioritize carat size as the most important factor when making selections. CUT determines the sparkle of a diamond NOT carat weight. If you don’t want to commit the same shopping mistakes others had made, you need to check out this proven method of choosing a diamond with the best sparkle and brilliance.
All in all, the “diamond mm to carat” charts are useful in providing you with a rough idea of how big the stone would look on a finger. To complete the selection process, you need to go beyond the 4Cs that are shown in a grading report.
Finally, did you know that you can decipher some hidden details about a diamond based on its weight alone? On the next page, we will show you how to reverse engineer and perform critical analysis when you go shopping for diamonds.
How do you tell how many carats a diamond is? If the size of a diamond is 6.61 x 6.63 x 4.02 (1.07 ct round), how do I know if these parameters are actually good for this particular diamond?
To answer your first question, you can tell how many carats a diamond is using mathematical formulas to derive a somewhat accurate estimate.
For your second question, you don’t. Numbers only reveal some minor details of the actual diamond. It’s much like going on a blind date with someone on the Internet where you have no idea what the character of the person is like. Is he/she kind, generous, compassionate or honest? Or would he/she be deceitful, inconsiderate or self-centered?
You should read these articles:
I’m using the diamond size comparison as a guide to buy a 2 carat diamond. I’m torn between an Asscher and an oval cut. The jeweler showed me an asscher that measures 7.5mm by 7.5mm and I confirmed this with the grading report information.
The pricing was quoted to me as $11,500 before taxes. Is this a good deal?
He also showed me a 2 1/5 carat oval diamond and based on the oval diamond size chart you provided, the dimensions seem a little off.
Choosing a beautiful fancy cut diamond cannot be done based on dimensions or grading reports alone. While dimensions can help you weed out badly cut stones, you should view (magnified) photographs/videos to determine the personality of the diamond. The overall outline, locations and types of inclusions are all factors that play an important role in its appeal.
Also, you should view ASET images when selecting a fancy cut diamond in order to determine its optical performance. For shapes like ovals, marquises and pears, it is best to seek the help of a professional to determine the extent of the bowtie effect. If you intend to buy a fancy cut diamond, this guide is indispensable.
I’ve only included an arbitrary 2ct size for the oval diamond carat chart. You can try to estimate and extrapolate the extra 1/5 carat weight. I want to emphasize that this is an estimated weight and for fancies, some deviations from the figures are OK. What ultimately matters is the cut quality and performance of the diamond.
I don’t get the part about diamonds having the same carat weight and at the same time, having different sizes. Why does this happens?
Carat refers to the weight of the diamond and not the physical dimensions it possess. Two diamonds’ dimensions can differ even though they have the same weight. For example, a 1 carat round diamond that is ideally cut will measure up at 6.50 mm. On the other hand, a 1 carat diamond that is cut deeply could have a diameter of 6.20 mm.
Illustration of two 1 carat diamonds to relative scale.
Also, most people have misconceptions that a diamond of 3.00 carats would be twice as big as another stone of 1.50 carats. This isn’t true. As you can see from the diamond size comparison above, a 3.00 carat diamond would have a diameter of 9.00 mm compared to the 7.50 mm diameter a 1.50 carat diamond has. The 3 carat stone is only twice as heavy and not twice as big!
I’m wondering how big would the different carat sizes would look in relative proportions to different ring designs. How do you tell how many carats a diamond is? Would you be able to help?
The best way is to head to your local jewelry and ask to see some rings. You can learn how to tell how many carats a diamond is through experience and I personally gained my knowledge through trial and error as well.
You can also do this online at James Allen. Simply head our to their engagement ring setting listings and click on the images of “previously purchased rings”. E.g. https://www.jamesallen.com/engagement-rings/solitaire/14k-white-gold-2mm-knife-edge-solitaire-engagement-ring-item-7115
You will be able to select the corresponding shape and see how they look like in that particular setting.
From top to bottom: 0.70, 1.01 and 2.40 carat round cuts on 2.5mm platinum rings.
To see engagement rings that other people had purchased, you can also click here to check out our image gallery.
What is the length and width to hight ratio in fancy cut diamonds? Also, I am trying to find out how big is a 1 carat diamond compared to a 1.25 ct stone.
You can extrapolate the dimensions on the chart and calculate how big a 1 carat diamond is compared to its 1.25 carat counterpart.
To answer your next question, you can see the l/w for the respective shapes in the corresponding shapes by using the navigation menu above in the header.
I am looking for a plastic “Heart” diamond or gem sizing chart with punched out sizes to match up diamond heart solitaires to get an approximate sizing on solitaire rings I have. Where can I purchase one please?
You can try purchasing loose CZ diamonds from eBay or simply print out the chart here on plastic sheets and cut it out.
I’m wondering if a mark in the head of my diamond ring that measures about 9-10mm. Is a size for the setting? It is clear and sharpe 10. The normal marking for gold purity are on the band. This is a full bezel head solid. Easy to read and it is not the carat weight. Do you know if the head size, is ever marked in the head of the ring? Thx
The head size of the ring is usually not marked.
I like your whole website! Your content would fill easily more than a book of more than 400 pages:-).
By studying many of your pages I also found another website, very small after I have read this page about carat size. It’s content is about face-up-size of a diamond. Their headline might be about: “A diamond must look its weight.”
I am able to compare diamond sizes.
Now I am wondering and ask you if these datas are of any use for consumers like me? Their result: if I compare 1 carat round and 1 carat Princess I receive face-up-size in mm and in mm/ct. On one nice image view I can identify the different face-up-size between them and also by comparing round with other fancy cuts.
All in all I am gaining diamond knowledge here and it will take some more weeks to be fit enough.
Measurements are only one of the aspects of well cut diamonds and don’t necessarily mean anything. If your priority is in light performance and brilliance, scope images like the ASET and Idealscope are the most important data to analyze. They hold tangible data compared to useless figures.
Hi Paul, im looking to buy my wife a pair of diamond stud earrings for our 25th anniversary. can you advise what cut and size would be the best. I’m looking at a 0.75 to 1 carat per earring. there are also so many options regarding colour and purity what would be the best on price?
This blogpost here will address many of the questions you have: https://beyond4cs.com/earrings/choosing-the-best-diamond-studs/
Your chart only goes up to 5ct for the various shapes. I would like to know how big a seven ct engagement ring would look like.
You can actually see photographs of how 7ct rings will look like on the hand in this article.
I’ve been shopping for a rose cut round diamond. My question is being that the bottom of the diamond is flat does the dimensions of the crown or the girdle affect the apperance of the diamond? I’ve seen stones less than one carat and some closer to two carats both 8mm. Just wondering what a ideal ratio is for rose cut, not really able to find much info online. Thanks in advance!
The dimensions of the crown would affect the appearance of the diamond. The thickness of the girdle doesn’t have such a big impact in terms of performance. With rose cuts, there isn’t an ideal ratio per se and it would have to depend on a case by case basis. It’s the same with fancy shape diamonds. The dimensions I listed here says nothing much about appearance and performance. It’s just a general guideline to help people visualize carat sizes.
Hi! My hubby wants to upgrade my .91 ct excellent cut /SI2 ring to a bigger version. What is an ideal carat size for finger size 5? No larger than 1.4 ct though. Please advise.
For a size 5 finger, anything between 1 to 1.2ct would be ideal without being too flashy. Read this if you are shopping for a 1.4 carat diamond and it should guide you through some things to look out for.
Hi Paul, follow-up question on your recommendation of 1 to 1.2 carat for my size 5 finger. My current ring style is a platinum solitaire flare. Do you still think that 1-1.2 would be a good size with the flare?
I would still think so. Carat size is largely up to personal preference. What I think may be OK really means nothing. What’s important is that you are happy with the size.
Hi Paul, what do you think of lab grown diamonds? It is now very much in ‘fashion’ due to the fact that they are responsibly made and earth friendly.
Lab grown diamonds are gaining popularity because of the rise of ESG values in the corporate world and consumer interests. It all depends on your mindset and what you prefer although I would say that most of the better cut diamonds are usually found in the natural diamonds niche.
This is a great chart! I was looking for a diamond size chart and this is perfect.