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).
Actual Diamond Sizes on Hand of a 1.55 Carat Diamond
This 1.55 diamond will look about the size indicated in the picture, on a typical woman's fingers. A typical round diamond with a 1.55 carat size has a width of 7.6 mm; bear in mind that this can vary slightly depending on the cut. The picture shows a ring which is US size 6; this is the same as an L 1/2 ring size in countries like Britain and Australia.
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Also take into account the length and breadth of your fingers.