The depth and table percentage are two other measurements that affect a diamond’s brilliance and sparkle. Marquise: length to width ratio of 1.85 – 2.0ĭiamond Proportions and Appearance Anatomy of a diamond.Pear: length to width ratio of 1.45 – 1.75.Oval: length to width ratio of 1.25 – 1.5.Emerald: length to width ratio of 1.3 – 1.4.Cushion: length to width ratio of 1.0 – 1.08.Princess: length to width ratio of 1.0 – 1.04.Round: length to width ratio of 1.0 – 1.05.Diamonds within these ranges will be the most proportional and elegant: Rectangular and oval-shaped diamonds should be longer than they are wide, with length to width ratios ranging from 1.25 to 2.Įach diamond shape has a range of ideal length to width ratios. The length and width of round and square diamonds should be almost identical, giving them a length to width ratio close to 1.0. The ideal length to width ratio varies depending on the diamond’s shape. The 0.82-carat emerald-cut diamond shown above is 6.24 mm long and 4.41 mm wide, so it has a length to width ratio of 1.41. The ratio calculated by dividing a diamond’s length by its width. Length to width ratio describes the proportions of a diamond–whether it’s perfectly round, square, oval, or rectangular. The length to width ratio of 1.41 gives this emerald-cut diamond its classic rectangular shape. For square-cut diamonds like princess, cushion, and asscher, 1-carat is typically 5.5 mm and a 1.25 carat is 6 mm.Ī 0.82-carat emerald-cut diamond from Blue Nile. A 1-carat round diamond is typically 6.5 mm, while a 1.25-carat round diamond is 6.8 mm. These measurements are roughly comparable to carats. One carat is equal to 0.2 grams, so a five-carat diamond weighs one gram.Ī diamond’s size is described in millimeters (mm). A diamond’s size is how large the diamond will look when viewed from above, while carats describe how much the diamond weighs. When it comes to a diamond’s measurements, carats and size are two different things. The vintage-style asscher cut diamonds have a smaller surface area, so they will appear smaller than round diamonds, despite weighing the same. A 1-carat asscher-cut diamond is 5.5 mm across, while a 1-carat round-cut diamond is 6.4 mm across. Carats and Diamond Size Compare the size and weight of the asscher-cut diamonds (on the left) to the round cut diamonds (on the right). With a little research, it’s easy to find a diamond where all of these factors work together to maximize the diamond’s beauty. A diamond’s measurement is more than just carats–consider its shape, cut, and length-to-width ratio as well. Use this information as a starting point for estimating weights.If you’re shopping for the perfect diamond, think beyond the carats. Just keep this in mind: don’t take these figures too literally. For example, some charts list a 0.25-carat round diamond as measuring 4.1 mm. There are subtle variations to these values. (If you know your gemstone density values well, you can estimate the weight of a standard size gem by sight). The opal, with an SG of 2.15, will only weigh 0.61 carats. The sapphire, with an SG of 4, will weigh 1.14 carats. The diamond, with an SG of 3.52, will weigh 1 carat. For example, a 6.5 mm round diamond, sapphire, and opal, all cut in the same proportions, will all weigh different. The density or specific gravity (SG) of the material will also affect the weight. Thus, they’ll weigh more than the sizes on the chart. Typically, gem cutters cut colored gemstones with greater volume than diamonds. The carat weights given for standard gem sizes in the following chart apply to diamonds cut to ideal proportions. Over one carat, a 0.2 mm variance can usually be accommodated, sometimes more.

As a general rule, gems under one carat can fall within 0.1 mm of the setting size. For other shapes, metalsmiths must consider a variety of factors. For example, any round gem can be put in a standard setting. A skilled metalsmith can modify a standard setting to accommodate a variety of gem sizes. No, a gem doesn’t need to be the precise size of the jewelry setting. Do Gems Need to Match Standard Settings Precisely? However, in other circumstances, the gem’s value doesn’t justify the cost of a custom setting. You can then pay for a custom setting later. Under some circumstances, the stone’s value makes cutting for maximum yield worthwhile. Choosing a Standard Setting or a Custom Setting Emerald-cut tourmaline, 4.52 cts, slight color shift. It has a range of standard gem sizes for mass-produced jewelry settings. Although named after the emerald, which often receives this rectangular cut with trimmed corners, the popular emerald cut design can be applied to many gemstones.

Diamond dimensions 1