Diamond weights are stated in metric carats, abbreviated “ct.”
One metric carat is two-tenths (0.2) of a gram—just over seven thousandths (0.007) of an ounce. One ounce contains almost 142 carats.
A small paper clip weighs about a carat.
The metric carat is divided into 100 points. A point is one-hundredth of a carat.
Furthermore, the carat weight is measured to the thousandths and rounded to the hundredths
Some diamond carat weights are considered "magic numbers." Why? Because their carat weight falls at exact or greater than the most desired weights and sizes of diamonds. All other quality factors equal means that there is a price premium for these weights. For example, half-cart, three-quarter carat, one-carat diamonds and so on exhibit these characteristics.
See below for examples:
Generally, the difference between a 1.00 ct. diamond and a 1.05 ct. diamond will be nearly impossible to differentiate with the naked eye. Expect to see a slight difference in carat weight as the size increases by 5% or more.
Use the interactive tool below to compare the difference in size between carat weights and magic numbers.
Subtle differences in carat weight can dramatically affect diamond value. Two diamonds of the same color, clarity, and cut can differ in value based on carat weight alone