Here is a guide to decide what length chain would be best for you. 

This varies based on the size of your neck and your height, so keep that in mind. 

16 inches: Fits tightly against the base of the throat, like a choker. 

18 inches (average length of our chains): Sits around the middle of the collar bone. 

20 inches: Sits in the middle of the breast bone. 

24 inches: Sits around the bust area. 

30 inches: Sits just below the bust.