Diamond Carat Size Chart – (Weight to MM Visualization)

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.

Round Diamond Size Chart

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.

round diamond size chart

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.

Printable Carat Weight to MM Chart: Here’s a free diamond sizing chart that you can download and print out for your convenience. All images are drawn precisely to scale for A4 sized paper printing.

Visualizing And Comparing Diamond Sizes on a Hand

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…

finger simulation with different carat sizes

Visualize Fancy Cut Diamond Sizes in MM

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…
length to width ratios of heart cut diamondsIn 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.

Don’t Forget: Download your printable carat size chart that you can easily carry around to visualize and perform diamond size comparisons. This chart is an accurate representation of carat weight to mm dimensions.

Princess Cut Diamond Size Chart

princess cut diamond size chart

Oval Diamond Carat Size Chart

 diamond mm chart for ovals

Cushion Cut Diamond Size Chart

size of diamonds for cushion cuts

Marquise Diamond Sizing Chart

marquise diamond size chart

Pear Shaped Diamond Size Chart

actual diamond size chart drawn to scale

Emerald Cut Diamond Size Chart

carat scale for diamonds rectangular

Asscher Diamond Carat Size Chart

actual asscher carat size in mm

Radiant Cut Diamond Size Chart

 carat size to mm for radiants

Heart Shaped Diamond Sizing Chart

size of diamonds - heart shape

Download your printable carat size chart (scaled accurately to A4) and use it as a convenient reference when you go shopping for an engagement ring.

How to Use the Diamond Size Chart Correctly?

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.

   
   

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.

We highly recommend online jewelry vendors like James Allen and White Flash because you will get a better bang for your buck. More importantly, you are provided with tangible cut performance data and in-depth diamond details.


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18 Comments

  1. Shane-
    November 9, 2015 at 1:53 pm

    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 good for this particular diamond?

  2. Paul Gian-
    November 10, 2015 at 1:57 am

    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:
    http://beyond4cs.com/shapes/round/ideal-proportions/
    http://beyond4cs.com/2014/12/aset-reference-charts/
    http://beyond4cs.com/buying-diamonds-blind/

  3. Colbert-
    November 13, 2015 at 2:23 am

    I’m using the diamond size comparison as a guide to buy a 2 carat diamond. 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?

  4. Paul Gian-
    November 28, 2015 at 10:54 am

    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.

  5. Julia C.-
    January 21, 2016 at 12:33 pm

    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?

  6. Paul Gian-
    January 22, 2016 at 8:45 am

    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.

    hidden weight

    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!

  7. Carol-
    January 22, 2016 at 2:48 pm

    I’m wondering how big would the different carat sizes would look in relative proportions to different ring designs. Would you be able to help?

  8. Paul Gian-
    January 22, 2016 at 2:51 pm

    The best way is to head to your local jewelry and ask to see some rings.

    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.

    70 pointer SI2 solitaire round

    1.01 carat round diamond

    2.40 carat stone size estimation

    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.

  9. Hilal Rebai-
    October 1, 2016 at 8:45 pm

    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.

    Thanks

  10. Paul Gian-
    October 3, 2016 at 4:07 am

    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.

  11. Debra Curry-
    March 17, 2017 at 1:00 am

    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?

    Sincerely,
    Debra Curry

  12. Paul Gian-
    March 17, 2017 at 7:20 am

    You can try purchasing loose CZ diamonds from eBay or simply print out the chart here on plastic sheets and cut it out.

  13. Kathleen-
    April 12, 2017 at 4:51 pm

    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

  14. Paul Gian-
    April 13, 2017 at 1:40 am

    The head size of the ring is usually not marked.

  15. Torsten Kroeger-
    May 13, 2017 at 10:40 am

    Hello Paul,
    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.

    Sincerely,
    Torsten Kroeger
    Stuttgart, Germany

  16. Paul Gian-
    May 15, 2017 at 3:39 am

    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.

  17. Bert Edge-
    July 9, 2017 at 5:38 am

    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?

  18. Paul Gian-
    July 9, 2017 at 10:36 am

    This blogpost here will address many of the questions you have: http://beyond4cs.com/2017/06/choosing-the-best-diamond-stud-earrings/

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