Size plays an important role in determining the value of pearls.
The principal measurement of a pearl is the diameter of its round part. For any shape other than round or near round, it is common to measure both the vertical and horizontal length of a pearl.
Measurements are stated in (mm) millimeters or Japanese standard length,
bu (1 bu = 3,1 mm) .
Indonesian South sea pearls fall in a range of 8 to 16 mm. Exceptional specimens measuring up to 20 mm.