The most common sizes for Tahitian pearls are from 8mm to 14mm. Some are up to 16mm, and very rarely over 18mm. The largest known Tahitian pearl measures 21mm for a round pearl and 25mm for a semi-round pearl. A general gauge is, the larger the pearls, the more valuable they are.

Tahitian pearls may be found in the following shapes:
• round
• semi-round
• semi-baroque
• baroque
• ringed or circled

The round pearls are the most desirable and valuable, however the more unique shapes have a growing demand and special contemporary appeal. 

The most valuable, perfectly round Tahitian pearls are rare and the availability is extremely limited.

Semi-round Tahitian pearls are nearly round.

Semi-baroque Tahitian pearls are defined by four shape categories: drop, button, pear and oval.

Baroque Tahitian pearls are defined as irregular shapes.