The princess necklace is 17 - 19 inches in length....

The princess necklace is 17 - 19 inches in length. The most common length for pearl necklaces, it is well suited for wear with crew and high necklines. It also complements low, plunging necklines. Because 18 inches is considered the classic length for pearl necklaces.
Pearl Necklace Lengths and How They Wear - Pearl Paradise
https://www.pearlparadise.com/pages/learn-about-necklace-lengths