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).
1.55 Carat Diamonds
A diamond with a weight of 1.55 carats is equivalent to a 155 point diamond.
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Diamond carats, points and normal units of milligrams can all be converted between - this 1.55 carat diamond for example weighs 310 mg.
Diamonds that weigh 1.55 carats are typically 7.57 mm across their widest part.
A way of using numbers to help you compare diamonds is to calculate the cost per carat of diamond. How big a diamond appears does not scale linearly with the carat weight of the diamond, which catches many people out.
A shop assistant may show you a one carat diamond and a one carat emerald stone next to each other, and point out how much larger the emerald stone is. This is because emerald is a much lighter material, so for a given weight of it, it will appear much bigger than for an equivalent sized diamond. Buying a diamond should really be about what you and your partner want, but if it's really important to you, know that the average diamond size in an engagement ring is about half carat, give or take.
It's interesting to note that while the small carat diamond (by small i mean one or two carats) may have only been discovered relatively recently, many of the spectacular large diamonds were found many hundreds of years ago, such as the regent diamond of france which was used by two of the king louis's, with a mighty size of 140 carats.
Wit must be foiled by wit, cut a diamond with a diamond. William Congreve .
Don't forget to think about other diamond characteristics such as diamond cut, which plays a critical role in determining the amount of light that gets into the diamond and the degree to which the diamond sparkles in light.