4C's Handbook - Diamond Shape

Diamond Education Handbook

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Years ago there were very limited choices for diamond shapes available for diamond engagement rings and diamond jewelry, modern advances in today's cutting techniques have created many different shapes. These shapes range from traditional round diamonds to the very popular asscher and princess diamonds. It's not enough to pick the shape that you like, knowledge of length to width ratios and diamond proportions can affect how the shape of the diamond looks and how the light is reflected. Read further in this category to know more about length to width ratios, we'll cover more about proportions in the Cut section.

Select your Shape

Every woman has different desires and needs that help determine what's the most appropriate diamond shape for them. A conservative or more traditional woman might lean more toward a round diamond while a more contemporary or edgy woman may like a princess cut. Regardless of what your personality is like, you can bet there is a diamond that will be perfect for you. At any point during your research feel free to contact a GIA Trained Andrews Jewelers Consultant and they'll be happy to find a diamond that's right for you.


The round brilliant cut diamond is named "brilliant cut" because it is the most brilliant and reflective of all shapes. Brilliant cut diamonds consist of princess, oval, pear, marquise, and heart. A brilliant cut diamond regardless of the shape is cut with the same facet patterns on the top and bottom of the diamond. This gives the diamond very similar reflective properties even though the shapes are different. A round diamond has been around for over 100 years however, advances in cut design have taken the shape to new and amazing limits.

Today you can purchase what is called an ideal cut diamond, an ideal cut diamond is one of the world's most perfectly cut diamonds and is only available in the round shape. A round diamond is the most popular shape and you'll always have more to choose from, this will give you a better chance at finding the right balance of price, color, clarity, and size. To view the worlds most perfectly cut round diamonds search the AAA Round Diamonds.


Next to the round diamond the princess cut is the most popular shape of diamond purchased. It's beautiful shape lends itself to many of the designer engagement ring settings that are on the market today and they look great when set. A princess cut will look slightly smaller than a round diamond of the same carat weight because princess cuts are cut deeper in order to form the shape. Princess cuts are available in square or rectangular shapes although the square shape is most notable when considering a princess cut diamond. To determine if a princess cut is rectangular or square you'll need to examine the length to width ratio.

For a princess cut to look square it should have a ratio of 1.00 and 1.10. When looking for a rectangular princess cut you should look for a ratio of 1.11 and greater. To view a brilliant collection of princess cuts search the AAA Princess Diamonds.


The emerald cut diamond has been around for many years and once was a popular choice for royalty and affluent people. Some of the most famous and valuable diamonds have been cut in the emerald shape. An emerald diamond is a member of the step cut family of diamond shapes, which include baguettes, Asscher, trapezoid, and bullet cut diamonds.The step cut diamond gets it's name because the pavilion has a series of facets that run parallel to one another to form steps. Emerald diamonds have fewer yet larger flashes of light while round and princess diamonds have more yet smaller flashes of light. An emerald diamond looks like a prism and a round or princess looks like a kaleidoscope. Emerald cuts should typically look rectangular in shape however can vary from thick squatty shapes to long slender shapes. It is purely up to the wearer of the diamond to determine what is best for them.

For a true emerald shape, look for a length to width ratio between 1.30 and 1.40. For a great selection of truly amazing emerald cut diamonds search the AAA Emerald Diamonds.


The Asscher brothers of Holland created the Asscher cut diamond over 100 years ago. In the beginning only the world's most affluent and powerful people could own an Asscher diamond. Now this beautifully designed diamond is available to anyone who appreciates its beauty. The Asscher cut is considered a member of the step cut family because the pavilion facets run parallel to one another in a series of steps. It is cut very much like the emerald cut except that the Asscher cut is square while the emerald is rectangular. When looking at an Asscher cut you'll notice that the diamond's cut seems to go on forever, this effect draws the eye into the center of the diamond. Because the viewer focuses intently on the diamond it is very important to select a diamond of at least an SI1 quality or higher when designing your diamond engagement ring. Inclusions in an Asscher cut diamond that is graded less than an SI1 will be easily seen to the naked eye.

An Asscher cut diamond looks best when it is very square. It is important to select a diamond that has a length to width ratio of 1.00 and 1.10. To view an amazing collection of Asscher cut diamonds search the AAA Asscher Diamonds.


The marquise diamond can be one of the largest looking diamonds when compared to other shapes of the same carat weight. There are many engagement settings that look good with a marquise, particularly ones set with trillians or pear shapes on the side. The style of setting that you choose can sometimes determine the length to width ratio for a marquise.

A well-cut marquise shape diamond will have a length to width ratio between 1.75 and 2.00.


The oval diamond has always been a favorite for people who have longer and more slender fingers. The longer length of an oval diamond will compliment a long and slender finger. The oval is considered to be a brilliant cut stone because it is cut very much like a round brilliant cut, this adds to the diamond's brilliance. Oval diamonds look great in a variety of length to width ratios and what you decide on is truly a personal preference.

For the most appealing oval shape you should choose a diamond with a length to width ratio of 1.30 and 1.70.


A radiant cut diamond is very much like a princess cut and most people find both equally attractive. The major difference between the princess cut and radiant cut is that the radiant cut has angled cut corners. Although the radiant cut is a beautiful shape it tends to look smaller than other shapes of the same weight. Be sure to find radiant's with smaller depth percentages to maximize the size.

There are no agreed upon guidelines for a radiant cut when it comes to length to width ratios. Some people like square radiants and some like rectangular. If you like a squarer look try to stay around 1.00 and if you like a rectangular look go as high as 1.50.


The pear shape diamond is considered a brilliant cut diamond and has very similar characteristics as the marquise cut. The diamond tends to look bigger than other shapes of the same carat weight and it also looks great with trillians or additional pears on the side of an engagement ring.

There is no set rule for what is the best length to width ratio for pear shapes, however a nicely cut diamond will typically be between 1.50 and 1.75.


The cushion cut diamond is a very unique diamond shape and looks great in today's vintage style engagement ring settings. The corners of the diamond have a gentle curve or rounded look and the diamond is cut with large facets that add big flashes of light. Cushions cuts are sought in square and rectangular shapes.

There are no agreed upon guidelines for a cushion cut because some people like a square look and some like a rectangle. For a rectangle, look for a ratio between 1.15 and 1.30, and for a square 1.00.


The heart shape is a diamond indicative of romance and passion. The heart shape diamond looks great in engagement rings and also looks great as a solitaire necklace. A good length to width ratio is critical when choosing a great looking heart diamond.

A perfect heart shape diamond should be between .90 and 1.10.