How Big Is A 9 Millimeter Tahitian Pearl?

We have this question a lot. About 25 Millimeters (mm) equals 1 inch. That means that a 9 mm tahitian pearl has a diameter of just about 3/8 of an inch. Six pennies stacked together is about 9 mm.

The picture below show various size black Tahitian pearls compared to a U.S. dime, a number 2 pencil and a ruler.