Quick and Easy Buying Guide
Carat weight: 1 carat = 200 milligrams = 6.5 mm diameter. Doubling weight doesn't double diameter.
Diamond clarity: FL/IF/VVS/VS = super expensive, near perfect. SI = best value if you can check a photo for obvious inclusions (defects).
Color: D-G = colorless, expensive, only if you have money to burn. H-J = best value. Can go lower in gold metal settings than white metal.
Cut: Better cut ratings let more light into a diamond, making it sparkle more. Very important property, don't skimp here.
Set a budget and minimum cut (Premium). Go J color for gold and I/H for white metals. Go searching for SI1/SI2 clarity diamonds at James Allen. Pick a diamond with small/no inclusions. Choose a ring setting and buy it risk-free (60-day returns).
1.90 Carat Princess Shape Diamond Sizes on Hand
The precise size of a 1.90 carat weight princess shape diamond will vary depending on the depth of cut, but is usually in the ballpark of around 7.6 mm along one of the straight edges of the diamond. If you've got a ring in your possession and you know the size, you can compare it to the US size six ring pictured - this will help you get a better idea of the diamond size shown in the photo. A good tip to follow is to use pictures like this one to initially narrow down your size range; then you can go into stores and try diamonds out in person, armed with this prior knowledge.
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If you're a male trying to work out the appropriate diamond size to get your other half, don't forget that the diamond will usually look much larger on her smaller, more petite hands.
