How to Measure Pearls

by Samantha Volz ; Updated September 28, 2017

The quality of pearls is judged by a number of characteristics, including size. While the relationship between the size of the pearls and the price can vary depending on the dealer, generally the larger the pearls are, the more they are worth. According to www.bemypearl.com, the largest pearl on record was more than 9.4 inches in length. Most pearls are measured in millimeters, ranging from less than one to more than 20. Whether you are buying or selling your pearls, be sure you can measure their sizes to make sure you are getting your money’s worth.

Measure the diameter of round pearls. Use the measuring tape to measure across one face of the pearl in millimeters.

Measure fancy pearls, or pearls that are other than round-shaped, by measuring both the diameter and length of the pearls. Measure the diameter at the widest part of the pearl and the length from the top to the bottom.

Express measurements in millimeters. For pearls that measure fewer than 10mm, round to the nearest 0.25mm. For pearls that measure larger than 10mm, express the size in the nearest 0.1mm.


  • Pearl strands are categorized by the smallest and the largest pearls on the strand, rounded to the nearest 0.1mm. For instance, one strand of pearls may be categorized as having 8.6 to 13.3mm pearls.

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About the Author

Samantha Volz has been involved in journalistic and informative writing for over eight years. She holds a bachelor's degree in English literature from Lycoming College, Williamsport, Pennsylvania, with a minor in European history. In college she was editor-in-chief of the student newspaper and completed a professional internship with the "Williamsport Sun-Gazette," serving as a full-time reporter. She resides in Horsham, Pennsylvania.