Diamond weight is measured in carats, a small unit of measurement equal to 200 milligrams. Each carat is divided into 100 points. Therefore, a half-carat stone may be referred to as a "50-pointer" or "50-points". Carat weight is the easiest of the 4 C's for gemologists to determine due to the use of highly sophisticated measuring equipment.
Two diamonds of equal carat weight might vary greatly in value depending upon their cut, color and clarity. This is important because when mounted, one diamond may appear larger than the other, although they actually weigh the same. If size is important to you, focus on diamond measurements as opposed to carat weight. Diamonds that look big for their weight may have reduced brilliance and fire so always insist on great cut.
An increase in carat weight does not produce the same increase in millimeter diameter. For example, there is a 25% increase in carat weight from 1.00 carats to 1.25 carats but less than 8% increase in diameter (6.5 to 7.0 mm). This concept, along with the increased price per carat, explains why prices increase dramatically in order to get noticeably bigger millimeter size.
Over 1 million rough diamonds must be mined before one is found that can be cut into a 1.00 carat finished diamond. Because large diamonds are so rare, they generally have a greater value per carat. If all other factors are equal, the heavier the diamond, the greater its cost will be. For example, the price of a two-carat stone will be several times higher than four 50-pointers of equal quality.
Images shown are approximate size.
When it comes to buying a diamond for that special lady in your life, whether it is an engagement ring, a pendant, a bracelet, or some classic studs, size isn't everything... but it’s a lot. If you choose a diamond that’s too small, she might have to pull out a magnifying glass every time she wants to admire it (and it’s not very impressive to all of her friends, either). If, on the other hand, you buy a rock that’s way too big, she may not wear it for fear of theft (plus, most women are wary of looking ostentatious). Choosing the right diamond requires a lot of thought, but if you follow a few simple guidelines, you should be able to pick the right stone for every occasion.
Consider the size of her fingers. If she has a fairly small ring size, a smaller diamond will look proportionate on her hand. Try to find a moderate balance between diamond color and clarity grades to see how much carat weight you can get for your budget. Also, bear in mind the width of your engagement setting. Find a carat weight that complements the setting nicely without overpowering it, and vice versa.
1. Under ½ carat. This size is really only okay for everyday diamond studs (earrings), a tennis bracelet, or a diamond necklace (not a pendant, a string of small diamonds…although each diamond should be up to ½ carat, not the necklace as a whole). While this size looks great embellishing a larger central diamond on a pendant or ring, it’s really too small to stand alone.
2. Up to 1 carat. Properly presented, a 0.5 – 1 carat diamond can work fine for an engagement ring, although this size is really better for a nice set of earrings. You can do a strand of stones for a bracelet or necklace, just be aware that it might detract from your lady’s natural brilliance.
3. Between 1 and 2 carats. Not too large and not too small, this tends to be the preferred size for engagement rings. You won’t break the bank and she’ll have an adequately sized sparkler to wow her gal pals.
4. Between 2 and 3 carats. Now you’re getting into pendant range. A stone this size sported solo on a bare neckline will make draw attention, but not detract. You can use it for a ring, but it could be considered a bit flashy. If you really want to give her an experience of wide-eyed awe, buy a matching set and make them into long drop earrings.
5. Over 3 carats. If her idea of a good diamonds is “the bigger the better”, then you can’t go wrong with anything over this benchmark. It may not be tasteful, but it will certainly garner attention.