The metric carat is divided into 100 points. A pt. is one-hundreth of a carat. An easy way to remember this is to think of carats as dollars and cents. They are even written the same way: $1.34 means one dollar and 34 cents, and 1.34 carats means one carat and 34 points.

The larger the stone the more limited the availability. Larger stones are quite simply rarer; this impacts the relationship between rarity and value. The scarcer something is the more it is worth. A larger stone doesn't just cost more, it costs more per carat.

A 1.00 ct diamond weighs the same as four .25 ct diamonds, but even if all the other quality factors are equal, the larger diamond is worth more than the sum of the four smaller stones.

To learn about diamond carat sizes, click here.