Pearl Size

The general rule is that a larger pearl is more valuable than a smaller one, but only under the condition that all remaining quality factors are equal. Size is not included in pearl grade system, but it’s an important quality factor of a pearl.

The measurements of a single pearl shall be expressed to the nearest one quarter of a millimeter for sizes below 10mm and nearest one tenth (.10) of a millimeter for sizes 10mm and above.

Single pearls:

Graduated strands: the measurements used to describe a graduated stand of natural or cultured pearls shall include the max diameter of the largest and the smallest. The measurements shall be expressed to the nearest .10 of a millimeter.

Uniform strands: the measurement used to describe a uniform strand of natural or cultured pearls shall be expressed in one half mm variations and stated as the minimum size, e.g., 6 – 6.5 mm.

Single pearls are measured in a different way than pearls on a string. Only the diameter of round single pearl is measured, while other shapes are measured for length and width or length, width and height. Drilled pearls are measured at a right angle to the drill hole; the same applies to pearls in a necklace.

Freshwater cultured pearls’ sizes range from 2mm to 15mm; the average size is still from 4mm – 5mm to 6mm – 7mm. Sizes of 8 – 9mm have increased over the last years but account for only about 0.01 % of production for really round shapes. Sizes of over 12mm are rare.

The size of South Sea cultured pearls is in the range of 7mm to 20mm, while the average size is 12mm to 14mm. sizes of over 14mm are rare and offer a certain guarantee for price stability, even for average qualities. The average size varies according to geographical areas:

Australia: 10mm to 20mm, average 12mm to 14mm;
Philippines: 9mm to 16mm, average 10mm to 12mm;
Indonesia: 7mm to 16mm, average 9mm to 12mm.

The size of the Tahitian cultured pearls ranges from 8mm to 20mm. The “Robert Wan Pearl” which is exhibited in the Perles de Tahiti Museum in Papeete, has a diameter of 20.92mm and weights 62.5 carats, is the largest round Tahitian cultured pearl. The average and the most popular size of the pearls is 8mm to 12mm. but within these years, sizes between 8mm to 11mm and 13mm to 17mm are selling best.

The size of Akoya cultured pearls is in a range of 3 mm to 10mm, the max size is 11.5 – 12 mm. but 10mm is rare. Size doesn’t have a stronger influence on the price of an Akoya cultured pearl than the other quality factors.