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A CARAT is the standard unit of measurement used to weigh diamond and gemstones. In nature, larger diamond crystals are relatively rare.


Consequently, as the size or carat weight of a diamond increases so does its value.

Carat refers to the size or carat weight of a finished polished diamond.  As the carat weight increases ‘per carat value’ is increased in relation to fixed categories of weight.

One carat (1.00 ct) equals 200 milligrams, or 0.200 grams.  You may also have heard jewellers talking about "points". In common jewellery terms, when referring to a diamond weighing less than one carat, jewellers use points, just like cents are used for prices lower than one dollar.   A point equals 0.01 ct. So, for example, a 15-point diamond is the same as a 0.15ct diamond.

The larger the diamonds, the more rare they are giving them a greater value per carat. The price of diamonds rises in relation to size.  Accordingly, a one carat diamond with a certain colour and clarity will be much more valuable than two separate half carat diamonds of the same quality. Due to higher demand, diamonds increase in value after they reach the half and full carat mark.

It is a common misconception that a half-carat diamond is half the size of a one-carat diamond. While a half-carat (or 0.50ct) diamond is half the weight of a one-carat (1.0ct) diamond, the size difference in round stones is only 1.35mm. The average measurements for a 0.50ct diamond and a 1.0ct stone are 5.00mm and 6.35mm, respectively.


Key Points:

  • Carat is specifically a measure of a diamond's weight, and by itself may not accurately reflect a diamond's size.
  • We tend to evaluate diamond size by viewing it from the top because that is how diamonds are presented to us when set into a ring.
  • To understand diamond size, carat weight should be considered in conjunction with two other criteria:
    • Distance in millimetres across the top of the diamond.
    • Diamond's cut grade.

BUYER'S TIPS - Which carat weight should you choose?

  • The best carat weight for a diamond often depends on the desired style, the size of the ring finger, the size of your setting, and your budget.
  • While the size of the diamond significantly affects its price, it does not guarantee beauty.
  • Before you buy a diamond, it is best to first make a decision about the quality you would prefer and then choose the size of diamond that you can afford in that quality range.
  • Remember that diamonds appear larger on smaller fingers. A 1.50 ct diamond solitaire will look bigger on a size L finger compared to a size Q finger.
  • If you prefer a 1.00 ct diamond but are limited by your budget, consider a 0.90 ct one. Size difference between 0.90ct and 1.00ct diamonds is only very slight to the untrained eye. A well-crafted 0.90ct diamond will have more sparkle, fire and brilliance than a 1.0ct diamond for the same price. This same argument also applies to other diamonds of comparative size ratios.