Diamond Carat Weight Chart

What a Diamond Carat Weight Chart Is

A diamond weight chart compares sizes, weights, and diamond shapes. The charts also break down diamond carat measurements into smaller units, points. Intuitively, more carats equal a bigger size and a higher number of points.

Jewelry Days has a great visual chart that lists the shape of the diamond, millimeters, carat weight, and points/cents. For example, the ideal proportions for a one-carat oval cut diamond are 7.5 x 5.5 millimeters, 100 points. A one-carat emerald cut diamond will still be 100 points, since points are based on number of carats, but the measurements should be 7 x 5 millimeters. A pear shape diamond of the same carat weight and points would ideally be 8 x 5 millimeters.

According to Jewelry Days, one carat is 100 points, half a carat is 50 points, one quarter carat is 25 points, and so on. One carat is also 1/5 gram. Since 1913, the way of measuring one diamond against others has been the same: a carat is one-fifth of a gram.

Normally, you'll see diamonds listed in quarter increments rather than points or millimeters because they are easier for consumers to relate to.

Round Brilliant Cuts Work Best

Diamond carat weight charts work best on round, brilliant cut stones, though some charts, as the one listed above, will compare a number of different cuts. It's easiest to determine the diamond carats based on the diameter of a round stone rather than that of a pear shape, for example.

Other Gemstones

Don't use a diamond weight chart for other gemstones; they don’t work exactly the same. All gemstones aren't the same density as diamonds. A sapphire that measures the same number of millimeters across will not weigh the same as a diamond of the same width, for example. It’s a common misconception that a gemstones physical size is equivalent to its carat value, when in fact carats are a measure of weight rather than dimensions.

Applying the Concept

While it's great to know that if you have a one-carat diamond in mind, it's 6.5 millimeters in diameter, that might not tell you much if you're ordering a ring online. It could be hard to visualize. Blue Nile offers a solution, a visual representation. Don't take it too seriously, since the picture will show up differently on different monitors. The Blue Nile page also offers suggestions for choosing a carat size based on the ring size and budget.

A Final Note About Charts

Charts are helpful if you're curious about how one diamond shape or size compares to the next, but if you're about to buy a diamond engagement ring, you'll need to think more along the lines of the shape she'd like, the clarity you prefer, the color of the diamond, the setting, and what you can afford.

When a chart comes in handy is when you wish to determine how big a two-carat center stone will look against your significant other's hand, for example, because it gives you the diameter in millimeters. It's better, if possible, to allow your soon-to-be fiancé to try on rings with diamonds of various sizes in different settings. However, that may not be possible if you want the proposal to be a surprise.

What looks small on one hand may look large or just right on another. It's hard to take a millimeter measurement given to you by a chart and mentally determine how it will look in a specific setting on someone's hand, but a diamond carat weight chart can be a useful tool as you begin planning to buy an engagement ring.